I have a JD 2305 and I am running the bx42 on it. It runs very smooth and does not bog down the motor at all. The rep that sold it to me (an ex-mechanic) stated that the bx42 will run more efficient on my tractor because of the larger fly wheel. It will actually use less horsepower to keep it going than the smaller bx35.
I have not pushed the unit with much hard wood but I am confident that it would chew up almost anything that I put in it.
I am not sure if there is a difference between the bx42 and the bxm42 so make sure we are talking about the same unit.
Good luck.