Tim Baker found that 65 grains of weight at the tip of a selfbow will slow it 1 FPS. I have used the fake snakeskins once and I don't remember them being anywhere near that heavy and most of the weight was not at the tip. Based on this, I would say the answer to your first question is no.
I would not do the belly.
Fake snakes look fake in my opinion. They don't look awful but it is pretty obvious that they are not real. If I had a nice bow, I would not put them on there.