Skeletar, castor armor only works if the castor is showing outside the chassis, where it can actually protect the chassis. If the chassis surrounds the castor, it becomes useless.
Well one of the basic rules in RA2 is : Anything attached directly to the chassis cannot be destroyed (infinite hitpoints i think).
EDIT: Weirdo, Jugglers do not use flippers to get opponents onto their weapons, they just use wedges.