If you can get a manual, there should be a reference demension to tighten the bolts to. I have had machinist friends make me guages out of a piece of stock say about one inch thick or whatever is called for. Much easier than using a rule.
FWIW, I had sold a batwing to my neighbor during the off season. I told him to go over the slip clutches before he used it but he did not. First time he used it, he chose to take out a thicket. Tore up one of the wing driveshafts pretty good. He learned a costly lesson.