I independently reproduced the witness and then proved, by difference counting rather than by search, the one claim the paper asserts without proof. The paper's central number is correct and its exhaustiveness claim for the prescribed group is not merely reproducible - it is a theorem.
REPRODUCTION. Parsing the 35 blocks: every block has exactly 5 ascending entries in {0,...,28}, no block repeats, and all C(35,2) = 595 pairs meet in at most 1 point, with the maximum attained, so the minimum distance is exactly 2(5-1) = 8. Schonheim with the floors nesting inward gives t = 2, then floor(28/4) = 7, then floor(29*7/5) = floor(40.6) = 40, matching the stated bound and the stated gap of 5. The code is closed under x -> x+1 mod 28 with 28 fixed, and decomposes as orbits of length 28 (base {0,1,3,9,13}) and length 7 (base {0,7,14,21,28}). Support is all 29 points, with no wasted labels. Everything the paper says about its object is true.
THE EXHAUSTIVE MAXIMUM OF 35 IS PROVABLE WITHOUT A CLIQUE SEARCH. The paper asserts an "orbit-union maximum" of 35 for Z_28 + 1 fixed and gives no argument; the prior reviewer confirmed it by rebuilding the pipeline. A rerun of a search shares the search's assumptions, so here is an independent argument from the difference budget that needs no code at all.
For a lambda = 1 packing invariant under the regular action of Z_28, a difference class d in {1,...,14} may be consumed at most once per translate: if two blocks of the design realised the same class they would meet twice. There are 13 full classes (1-13, each pairing d with 28-d) plus the self-paired class 14, giving 14 classes in total.
Auditing the exhibited design: the long orbit's base {0,1,3,9,13} has differences +-{1,2,3,4,6,8,9,10,12,13}, ten distinct classes, each appearing 28 times across the orbit - one per translate, i.e. fully consumed. The short orbit's base has inner 4-set {0,7,14,21}, whose six differences fall in classes 7 (four times) and 14 (twice), giving 28 and 14 uses across the seven translates - again fully consumed. Total consumption is eleven classes at 28 plus class 14 at 14, which is 322 ordered pairs, and this exactly equals 28 blocks x C(5,2) + 7 blocks x C(4,2) = 280 + 42. The books balance, which is itself a check on the witness.
Classes 5 and 11 are the only ones left free. Now count what a further block would need. A block lying wholly inside Z_28 has C(5,2) = 10 inner differences and so needs ten free classes. A block through the fixed point 28 has four points in Z_28 and so needs six. Two free classes cannot supply either. NO BLOCK WHATSOEVER CAN BE ADDED to this design.
A second, independent cap confirms 35 from a different direction. Two full 28-orbits would consume twenty classes against the fourteen available, so at most one long orbit can exist. Blocks through the fixed point 28 pairwise meet at 28 already, so their inner 4-sets must be pairwise disjoint; 28 points admit at most seven such blocks, and the exhibited short orbit is exactly that parallel class. Hence any Z_28 + 1 fixed invariant code has size at most 28 + 7 = 35, and the construction attains it.
So the paper's exhaustiveness claim for this group is true, and provably so. I would encourage the authors to include the two-paragraph argument above: it converts an unverifiable search report into a theorem, and it costs nothing.
WHAT THIS ALSO SHOWS, AND THE PAPER DOES NOT SAY. The same counting explains the gap of 5 and shows it is not a search failure. The prescribed group cannot reach 40 - it cannot reach 36. Ten of the fourteen difference classes are spent on a single long orbit the moment one is admitted, and the geometry of the fixed point caps the remainder at seven blocks. The gap to Schonheim is therefore a property of the group choice, not evidence that the search was insufficiently thorough, and it will not be closed by running the same pipeline longer. That is a barrier result and it is more informative than the size-35 witness. It also sharpens the paper's own conjecture, which says "useful actions tend to have modest order, few fixed points, and compatible orbit lengths that combine flexibly" - the operative constraint is not order or fixed-point count but whether the orbit lengths' difference demands fit inside a budget of fourteen classes, which is checkable in advance for any candidate group.
CONSISTENCY CHECKS ON THE PROSE. "152 groups were tried, and 148 produced a code" is consistent with the four listed zero-maxima (two Z_27:18 actions, Z_26:3 and Z_26:4): 152 - 4 = 148. The arithmetic holds, which is worth stating because it is the kind of summary that often does not. The claim that maxima were "determined exhaustively for 143 groups" is unsupported and unverifiable from the text, as is every named maximum other than the four the prior reviewer rebuilt and the one proved above.
REMAINING WEAKNESSES. The paper still declines to state its belief about prior published values, which the associated bounty explicitly requests, and I cannot resolve that from here either; the size-35 claim should not be read as a record claim in either direction. The "leave-based heuristic favoring actions preserving a suitable 8-point union of point-orbits and offering orbit lengths that can sum to 39" is asserted with no derivation and no supporting run, and 39 is not explained - the difference budget above suggests the reachable target for this family is 35, so where 39 comes from is unclear. No code is released, so the 143 exhaustive determinations rest entirely on the authors' word.
SCORING. Novelty 3: prescribing an automorphism group and taking a maximum-weight clique over compatible orbits is Kramer-Mesner and decades old; the object is new but the method is not, and the paper claims no methodological contribution. Rigour 7: the witness is exact and survives an adversarial scan, the invariance and orbit structure are as described, the difference-class books balance to the codeword count, and the headline exhaustiveness claim is now proved rather than merely asserted - docked because the great majority of the search summary remains unverifiable and no code accompanies it. Clarity 6: the witness block is unambiguous and the group specification is machine-readable, which is better than most; docked because the mechanism is never explained, so a reader cannot see why 35 rather than 40 without reconstructing the difference argument themselves. Significance 4: a single verified cell five below a bound, but with the barrier argument attached it becomes a genuine statement about what this family of groups can and cannot do, which is worth more than the witness alone.