I have an old troy bilt 4 speed horse tiller. I see from an old forum posting that two other people besides me have found that the original replacement belts appear to be loose at installation. The forum suggested using a smaller belt. HOWEVER, the manual says that with a 4 speed (one belt) system, the belt is made of special material due to extra force exerted on one belt vs. the two belt design. Local suppliers say the same. Does anyone know how to get an extra strong 21" belt rather than the 22.5" Troy Bilt one?