Not really design … just manufacture. Design is usually done in-house as far as I know

Sure. But the point still stands. All the data suggests that this is a minor issue at worst compared to all the other health and engineering challenges for Mars.

All of the research on this concentrates on returning to the relative hypergravity environment of Mars after the 6 month micro-G transit trip.

Even bedrest studies do not replicate the real microG environment because of the transverse loading on the bones that induces iconoclasts to maintain some bone mineral density.

Small 80# people don’t have issues with gaining muscle mass in 1G if they eat enough food and exercise.

All of this points to the fact that collectively the research strongly suggests that even a little bit of gravity is enough to strongly mitigate the historical issues with space flight in microG. So much so that NASA isn’t really too concerned with 1/6 long term. 1/3 gravity is barely a concern at all, except it being too high after a long Mars transit.

1/3 gravity would be pretty fine physiologically speaking. There is pretty decent data on this. The gravity would be the least of the problems on Mars.