Two nitpicksFLHerne wrote:More evidence that structural strength isn't much of a problem would be those LACs from HotQ - "No LAC crew could survive the sort of acceleration ships routinely pulled in hyper for the simple reason that their inertial compensator would pack up the instant they tried it." can't be referring to accel under impellers (because the LACs ought to be quicker than a BC in that case); the LACs must be being towed in a grav wave for at least part of the journey, complete with the multi-thousand-g accelerations involved.
1) We know from Honor Among Enemies, House of Steel (and the older Jaynes and SITS reference books) that no LAC before the ones Honor took to Selisia packed a powerful enough drive to max out its compensator. Those LACs (which would include the Masadan LACs) maxed out at about 409g - less than a most Superdreadnaughts.
But that's ok, a LAC under it's own impeller would still experience normal acceleration.
The second nitpick is that while the LACs were tractored, I don't think there was any grav wave between Masada and Grayson, nor do I think you could tow anything (other than a partially disabled starship that still had at least 1 sail) successfully along or through a grav wave.
But you're point that the hulls were stupidly strong is still correct. The text-ev is that they were, though like kzt I'm kind of at a loss for why they be build to strengths so far in excess of their needs. Sure sometimes construction is rigidity limited, not strength limited. To be stiff enough requires enough material to provide more strength than you need; but not thousands of times more...