How to use extra diameter of oversize variator?

Hey guys,

Last month got a naraku oversize vario to try out and hoped to atleast get my top speed back to 60 on Sinnis Harrier 125 (after 3 years use its average on flat is about 50-55 now). Was a bit put off by not noticing any improvement at all, was even a bit jerky taking off as the belt wasn't tight to the centre boss.

Anyway, I switched the vario plate back to original after a week and its been sitting in the garage since then.

I look at it and can see the belt outline with about a cm or 2 clearance from the edges, so if i stuck it back on, so how do i go about using up all the real estate?

I've been thinking about a slightly longer belt, plus some boss shimming. The current belt can go slightly closer to the centre boss than it already is for better acceleration, so maybe +1cm belt and +1-2mm vario shims?

Currently:
OEM belt 835-20-30
Rollers 12g? (worn, replacing with 12.4/12.8 next week) I believe OEM is 12.8g
OEM springs, I think 1500rpm

I have shims up to 3mm and there are 845-20-30 belts available I can see

Thanks!