43 is well corrected
I haven't put it to extreme tests but all the architectural shots I've done with the 43mm and 50mm and other Mamiya 7 lenses show that they are quite well corrected for geometry. Which would only make sense, as the 43, 50, and 65 are biogon-derived (improved?) designs, known for exceptionally good correction. They are what makes the 7 system so good, IMHO. A comparison vs. Biogon SWC would be interesting, as far as geometry goes. I suspect the Mamiya would more than hold it's own.