Interesting.... I would venture to guess they will compress down a bit more... maybe low .040" range ?? Are they a composite material like a typical Felpro? I'd still go with the 1121G's....that's worth about .2 point in Static CR. Get a little here and a little there and it'll add up.
BTW, I just looked back at you teardown pix of the 318 and noticed the valves have some very deep 'dimples' in them. I am willing to bet that those dimples shown are worth about 3 extra cc's of displacement per hole; I have measured 2 cc's on some less drastically dimpled valves. If you are doing the 302's see if you can dig up some flat faced valves out of your stash and reduce the chamber volume that way...with around .1 to .15 in CR. A little here, a little there.....every trick adds up.