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It looks like you have a little room up at the outside of the variator. If heavier weights don't get your RPMs down then I think you might consider shortening your boss a little. You could use a heavier clutch main spring to resist the climb, but if your belt wont go to the top of the variator, I see no way for your RPMs to come down at top speed other than to close the gap between the variator pulleys one way or another.

I'd find the biggest weights I could get and if they don't slow down your top speed RPMs then you know you have to do something to close the gap.

This shows us there is a market for different diameter rollers. It would be super if you could just buy rollers that are slightly larger in diameter. That being said, you could try sliders. They seem to increase the range of the variator over what a roller can do. I know some people say they "flip" but that would indicate that there was some point in their running when the variator was not being held tight against the sliders, allowing them room to jiggle themselves into a new position. That would also point to the need for a tighter main clutch spring.

What really matters for top end speed is how high the rollers can actually go. I found on my scoot that light weights opened the variator just as much as heavy ones. They were all heavy enough to fully open the variator. Changing the weights just changed my acceleration RPM and the RPM required to hold the variator open, but didn't change my top speed.

You can cut the boss 1mm for every 2mm radius you have left until you hit the highest point you want your belt to ride. It's actually closer to 1.75, but 2 is a good round number, so if you have 2mm radius to climb then you can cut 1mm off of the boss.

Chances are that if you cut the boss you can keep your weights low. That will allow you to tune your acceleration and cruising RPM with the weights, while the boss length will determine your RPMs at top speed by allowing your belt to go to the maximum height you want, thus taking maximum power from the engine.

As you know, if the belt goes too high, the engine may not be able to pull it, and you end up with a situation like I had, where even the lightest weights I could find would not allow me to rev high enough to get my top speed because my variator was too fat. I was going to shim it but I tried some sliders and they let the variator open a little more.

What would be ideal is if you could cut the boss to make the belt go all the way up, then have some 1/10th mm shims handy to bring it back down if you needed to. If you had a lathe you could just chop the boss off 1/10th of a mm at a time until you were happy with the performance. This is a fine balance between the HP of each motor and the variator dimensions. There's nothing wrong with shims. They are just another tool in our toolbox, like weights and springs, that we can use to tune our variators to match our engines and gearing. That reminds me of yet another option. You could up your gears. And another option, adjusting the variator face angle. At any rate, adjusting the boss is easier, cheaper, and more tune-able.

Me, I'd try the heaviest weights I could find, and if the RPMs were still too high, I'd shorten the boss by the calculation above, and if I went too short, shim the boss until I liked the overall RPM curve. It's cheap and highly tune-able that way. With a shorter boss and 1/10th mm to 1 mm shims you could try dozens of configurations for just a few dollars and it should work to your satisfaction. You'll get the max speed via the boss length, and the acceleration and cruising RPMs you want via the weights.

(I just saw your post about up gearing. I look forward to seeing how it comes out!)