I have over 50 hours of transmitter time on my ST .90. I switched the JR SM125s with titanium arms out for Hitec digitals with DuBro arms. Not a problem...except I have lost both elevator halves, the rudder and one aileron to hinge failure over several gallons of glow fuel with no crashes (whew).

The plastic arms are strong enough for a .90 size plane, but I would not go much bigger. If you run 3D throws, be sure and use the larger arms.

The ST .90 is a GREAT airplane!!