The last letter in QA42 "A" is for "adjustable" the center plate have 8 holes, use the narrow one but don't torque your bold completely, you install the belt and slide down the center plate as far you can to apply tension to the belt, now you torque your 4 center plate bold and adjust the belt tension with the side butterfly nut.
I remove the front thrower completely, I adjust the PTO adapter alone, much easy to deal with I think....It work for me
PS:Look in the manual for the "How to" adjust the bolt under the center plate.