If you take the dogs off a CS a 32" log can be milled with a 36" bar. If a "mount the Alaskan to the bar bolts and hold the bar at a bolt at the centre of the nose" method you can mill a 33.5" log with a 36" bar.
20HP for a 32": softwood is going to be overkill ie a lot of weight for not a lot of gain in cutting speed. Actual cutting times are often not as important as you think. Preping the log , refuelling and sharpening, living mills on and off the log, and handling lumber can be just as time consuming.
Of course if you don't have a medium/big saw on hand that is another issue.