I don't....I used a site that approximated the belt size based on 81"
6lb lower 3.1 upper , 1x 92mm idler, 2x100mm, 1x92mm
I had ordered 3 x100mm smooth but the guy said only the 92mm would fit next to the 6lb lower.
Are you thinking its slipping?
It felt tight as hell to me...what should...