last i knew he was runnin 21x12x8 (i think) 10 paddles.. i think i also remember him packin the front end quite a bit.. i dont think a +8 with 10 paddles with your 10mm is gonna cut it.
my 4mm cub with those same tires, the 10 paddles, wanted to bring the front end up pretty easily. i have a +4 on mine. i would say that +8 would be the very shortest you could go and still be able to launch it, but im thinkin +10 sounds better..