Can't answer your question directly, but am running a 25 ft 1020 with Crary Air Reel in 40-60 bu soybeans, on a 1660 Cummins. Engine power has been adequate at under 3 mph, but haven't pushed it more than that. 2009 harvest was late enough that green stems were not an issue.
We have an air reel on our 25ft head on our 2366, not sure how much of a difference the extra 5ft will make but in soybeans top speed is 3.5-4mph. It does make a world of difference with feeding though.