Has anyone tinkered with the variator? Such as lighter/heavier rollers, dr pulley sliders? Or the like and were your efforts successful or is it better to leave as stock?
Any comments Data?

Dr Pulley sliders are a no-brainer on every scoot, at least instead of OEM rollers at service replacement and potentially asap after buying.

Data will no doubt give the full info on simple spring changes, personally I'm not convinced the J Costa variator is worth the price though I've no personal experience, just seems expensive and poor return compared to sliders and air filter upgrades.

Cheers on that, what size and weight sliders would you recommend?

I took the standard 19gram rollers out of my burger and replaced them with 21gram dr pulley sliders

Strange! - usualy 10% lighter than OE...

Lighter gives faster acceleration. Heavier not as quick of mark but now sits at 70 mph at 5800 revs instead of 6800