Like Mr. Becker, I’d float the whole thing. And if you go up to the 1-1/8” Advantech, you’ll get much greater rigidity in the floor from panel to panel. When i was buying mine, the price difference was rather small, so went ‘big’! The Advantech decking has a 180-day weather warranty, which, to my way of thinking, means it can stand a whole lot of water for half a year. The amount of ‘water’ / moisture you’d get on the bottom of your panels through your slab has to be so minimal that the product would easily withstand it IMO. And I agree with taping the foam joints. Why not glue the Advantech T&G long edges? And stagger the field to a 50/50 ‘brick’ pattern, or a close to 50/50 as you can get. Maybe even a little glue on the short sides of the panels.
Best of Luck to you!
Don't let it bring you down,
It's only castles burning,
Just find someone who's turning,
And you will come around
Neil Young (with a little bit of emphasis added by me)
Board member, Gulf Coast Woodturners Association