[GeeTwo]

That certainly does work - that's how we did our robot last year. We used 6 inch mecanums and (I believe) the 10.7 TB minis Using 4 inch mecanum with the 8.45 is a bit lower, but that's good because you'll be carrying a heavier load and this is a slower-moving, though probably much faster scoring, game.
We were conisdering mecanum for our drive this year, but we were worried that the handling would change too much as we picked up the load (we're lifting outside of our chassis). The drivers even noticed it a bit just when we lowered our pickup arm on the practice 'bot (which was wooden and rather heavy) last year. We've opted for an H drive so that at least the direction of thrust will be what we expect, even if the accelerations shift a bit. We're figuring on putting the strafe wheel at the COG when we're carrying four or five totes (we're going to do up to six) so that it behaves well when carrying a full load (during scoring) at the cost of being a bit off-center when empty.