Just thought strap wrench with old belt ould provide better grip with leverage of the wrench if nut was really tight. Never tried just hiting the wrench with a mallet - will try next time. However when tightening I would feel more secure holding the pully than whacking it back tight. I did make a holding tool out of some scrap steel using a blown water pump to get the shape and holes right. Works a bit better than levering a screw driver across the bolts.