In many ways, this puzzle reminded me of the Ring Enlargement weekly puzzle.  The central question being: how many central hexes can we leave untouched?

I found two likely options for 42: with one empty hex on the less-spacious final-move orientation, and what you see here, with 2 empty hexes on the more-spacious last move.  I pursued this one more rigorously because it felt likely to be faster during early experimentation.

In addition, I could see that this general strategy suggested some 41A layouts.  I spent a lot of time trying to make one of them work, which ended up costing me in MechA.  Didn't hit the target myself, but would not be shocked to see someone else succeed.