[KirkEvil]

I think you should stay with the 3". Choking the motor and adding the hassle of adapting to the 2.5" to 3" is not worth gained clearance. It will have to be custom fabricated anyway right? That should get you clearance.

Also, 2.5" and 3" dont seem that different but if you look at cross sectional area its 4.91 sq. in versus 7.07 sq. in. Thats a gain of 43% cross sectional area even though its only 0.5" larger diameter! Much larger area if you multiply that by the length of pipe...