Highwayman, I shoot 4" vanes on Easton Slim Tech Axis HIT carbon arrows. I hunt in the rain and snow enough times that I've had feathers ice up where the vanes don't.
Longer vanes will stabilize an arrow better than shorter ones at the cost of a tiny bit of weight and faster deceleration due to increased drag (and, maybe, a teeny bit more noise?). No deer I've ever shot survived long enough to tell me I should have shot him with a little faster arrow. I'll pay the velocity price for the extra stability and forgiveness.
That said, I've used a Ripcord fall away rest since they came out, used a two prong fall away rest before that, and have never used a Whisker Biscuit. It makes sense that longer vanes would pay a velocity penalty with one.
Hope this helps.
Lance
