Question on rule <R3>
 

As per rule <R3(D)>An extension above 60 inches must fit within a 6 inch vertical cylinder.
Is it allowed for a part within this cylinder to flex outside of it when hit?

Re: Question on rule <R3>
 

Theoretically flex would not be allowed. You should build your robot robust enough that it will be in compliance.

But since an opponent cannot force you into a foul, in practice it would be unlikely to be called. (Unless it was your own alliance that bumped it outside the cylinder.)

Re: Question on rule <R3>
 

in my interpretation, yes so long as it is not intentionally designed to flex. But it shouldn't. What would you put up there that would flex? you don't want to be playing goalie with something flexible, you want something hard to bounce the ball back out.

Ask on Q&A. (Though I suspect their answer will be along the lines if "The 6-inch cylinder constraint is always in effect regardless of the state of the robot parts inside it.")

Re: Question on rule <R3>
 

I agree, if designed to flex then FRC might deem that Strategic because the design is specifically made to break a rule on a technicality.

Usually their strategic penalty is along the lines of Technical Foul, or if the rule already has a technical foul penalty, then a Red Card.