Mike,
(and others) -- there are some folks over at www.popupexplorer.com who have (in the "That Ain't Stock" and "Fix My Popup" forums) who have discussed and done this sort of installation. Look for tips from Everybodyhauls and Oz and Us in particular.
Yes, I read there. My beloved decided we needed to go the Popup route.
I've camped in it once now and like it a lot -- so much better than a tent -- but he and I both are still thinking we'd like to have a teardrop. But for now, I'm taking advantage of the chance to camp in the popup, 'cause it gets us out oftener than the tent did.