Well, that's a good question. Short answer, probably not very well. I don't use H/S stocks so forgive my earlier ignorance/answer.
CA (superglue) usually doesn't lend itself well to foam. There is foam safe stuff but it's not very good-especially for something like this.
I'd probably go with an epoxy. Something thin so that it'll wick into the foam's pores. Paint a layer on the foam, allow it to cure, then sand/machine it flat again, and then glue your pad to it. This way you have a hard/similar surface for the resin to bond to.
Good luck.
C