I think you answered your question in the other post on the 320GMT
These 300 series 1950 case style are all flat crystal. You clearly like the idea of a bracket so just go for it. Certain members are sensitive to the incorrect movement , to me its not really an issue and I really like the distinctive case of my 312.
Given the recent news of the replica P.9000 looking movement there may be some of the older style domed crystal models that might see the light of day, but quality yet to be determined.