We started harvest with a 3212 x20" on a 2388. Combine was light on the rear end even with 8 100# weight on the back. Pushing an 8x 30" on the 23 we could run 5mph in 200 bpa corn. Same yielding corn we usually ran 3.5-4mph with the 3212. You're taking in a lot more trash, especially this year when it seemed all the leaves were on the corn until mid Dec.
We leased a 7010 to finish harvest and the 3212 is a much better fit for it . I would think a 6088 would be able to handle a 12 x20" head but I also think you'd be better off with a 7088. Never hurts to have too much power. Even with the 7010 we ran into places the low engine rpm warning would go off. Several evenings when the dew was setting in the corn really got tough and at times we were down below 2mph unloading on the go. Lots of complaints this year in our area about lack of power of an evening.
Our original plans were to trade for a 6088 for next year but after running the 7010 we're going to purchase it, or a 7120, after the beginning of the new year. Lot's of features that we really liked on it compared to a 60/7088 plus is a little cheaper. Machine is an '08