Hi Nigel,
I assume you have a new tensioner as well and a rear flange IE/VX Aux DS Pulley? No rear flange it will not play nicely! I spaced my tensioner bearing with a packing part between the bearing and the mount tube to ensure the tensioner supported the full belt width. My non standard Monte belt guard from TMH needed some packing washers to prevent rubbing. I no longer remember on the Beta Spyder one, but I would have been looking out for potential rubbing when installing. On the Monte cover I have holes cut where the cam bolts might otherwise touch, but this is a thick GRP item.
Eric
PS I assume you have late series non flange wide cam pulleys because early ones can not run this belt. I have alloy Vernier cam wheels on both engines.