It's not stretch you need to worry about it's height. Yes, even with my taller tire, I *should* be able to run either an 18 or 20mm spacer in the rear. I haven't had the time to try a more aggressive spacer yet.

It would be even easier in your case since you're working with a slightly shorter tire; but again, it all comes down to camber settings, whether or not you're interested in rolling your fenders, etc. Either way, that proposed setup is still far from extreme.