I put potential on there
. Timing is more important, to me atleast, then how your arm structure is. You could swing the same racket with the same speed using straight arm and double bend, but either one could easily get more rpms/ mph on the ball.
Straight arm forehands are more centered around timing for power and consistency then double bend.
Btw OP, if you want more detail on straight arm/double bend, there are some really good posts if you search "straight arm forehand" and look