Whoa Mike! Nice job getting that Butcher Block off my shell! It looks perfectly flat, unwarped, and undamaged. Something I could never do when using a heat gun. Can't wait to see the drum you rewrap with that.
You pose a good question, and I'm waiting to see what the rewrapping experts say. We all have our favorite chemical or abrasive method of removing adhesives from shells (as discussed in this thread), but I haven't see much on cleaning the backs of old wraps. Unlike wood shells, I would imagine that just about any chemical stripper is going to eat into the wrap. What's left for options? Slow, tedious sanding?
Mike