I've run ty screws in my last 3 Mugens with no issues. The only place I don't use them is on the chassis braces because they tend to break there. Ty screws can save you a whole lot of weight if you use enough of them but they are more brittle. My rule is to replace as many srews as you can with ty then if one breaks put a steel one back in that (strees prone) location. The only problem I ever had with "galling" was strangly on the ty hinge pins in the A-arms (plastic). I'm still not sure I understand why that happened (every time).
-EMBX6,T8 1400, RX8, 5S Lipo ,Elite-RC, RCM tray
-EMBX6,T8 1350, RX8, 5S Lipo ,Elite-RC, RCM tray
-ROAR 4 cell rule Blows