I have a rudder/elev small model - which will fly inverted and the rudder does not "reverse" when flying inverted
imagine that
better get out the calculator and the airfoil charts It also climbs vertically FAST under full power to OSS in a veryfew seconds - power is a tiny CDrom motor on 11v 3 cell Lipo
rolls are rather barrel shaped- 275 sq in 7 ozs all up

the little bipe in question is apparantly setup incorrectly likely quite tail heavy as well as a mismatch on dihedral and effective rudder location and perhaps a rudder servo/linkage that is dicey