With no aero anything, and not really a very good TT position, I have the following for 3 TT's I did last year: 224w @ 21.7, 234w @ 22.2, and 243w @21.7. Note 20w increase in power (these are average power) with no increase in speed. No idea, but it was colder. So I would kill to do 25mph at 200w, but I think I would need closer to 300w to do 25mph on this course (which is rolling).