Removing glue residue?

I needed to remove foam knee pads on my royalex Wenonah Rogue. Those pads were glued down 25 years ago and they were still VERY attached. It was a chore just getting the pads torn off. What now remains is a layer of adhesive with a 1/16" layer of foam.
How can I safely clean all this off without damaging the hull?
Thanks in advance.

I'd bet WD40 might do the trick - often foam is secured to a hull with rubber cement....and I think WD40 should dissolve that adhesive.