1. Yes, I did stamp both sides of the bag. When doing so, you need to insert a piece of cardboard into the bag to avoid having the craft ink bleed through to the other side.
2. Yes, I heat set the bag with the SU! heat tool. Be very careful to hold the heat tool at least 6-8 inches away from the bag and use a swirling motion so that the heat will not be on any part of the bag for too long. I did this for 1-2 minutes total for both sides of the bag.