Haven't had issue with phillips stripping with high quality tools, but on my stock diffs set there was so much torque at one point it actually broke two of the screws inside the diff cup.
Might be....dunno. The flux bulks are a composite, as compared to the plastic on the X and SS, but I have no idea if they are stiffer or not - that's why I went with the FLM's.
Losi 8T 1.0, Savage Flux - XL style, LST XXL, Muggy, 3.3 E-Revo Conversion and sitting outside 425hp, 831 Tq Dodge Ram Turbo Diesel. It SMOKES
Well, you didn't actually have any problems with your diff's either!
Any plastic bulkhead, and some aluminum ones, will flex. If that flex occurs under power, one could potentially damage the gears. The design of the savage bulkhead itself is quite rigid, so IMHO, flex is probably low on the potential list of problems.
Losi 8T 1.0, Savage Flux - XL style, LST XXL, Muggy, 3.3 E-Revo Conversion and sitting outside 425hp, 831 Tq Dodge Ram Turbo Diesel. It SMOKES