A longer bow would certainly be a better match for your body size, but shouldn't be an issue with the rest problem. My guess is that the rest is being raised too early in the draw cycle so doesn't have enough time to drop away. It should raise to it's maximum height in about the last 1 1/2" to 2" of the draw cycle. If it's coming up too early you can possibly slide the cord attached to your cable up the cable a bit at a time till you get the desired results.

Another thing. If you're shooting cock-vane down try shooting cock-vane up.

It would be better if you post what your setup is; details. Then a more informed "guess" can be made.