Yes, leave the tape on while sanding... the tape is to draw highly visible lines to follow while you work.
When you finally do remove the tape, first be sure you at least slightly knock the corners off the edges with a sanding block or something, then pull the tape slowly at a very low angle, and do so working from handle towards the tip (important). Then work from handle to the other tip. You do this because the limb tapers in width, which violates/cuts through the fibers of the glass and when you remove tape from handle to tip, you're pulling away from those violated fibers, not pulling into and up on them. Going the 'wrong' way, pulling tape off from tips toward the handle makes it much more likely you'll grab those fibers and lift a nasty splinter of glass... which I did... once.