Who makes the best turntable belt?

I’m in need of a custom turntable belt made to the length I specify. This is because I changed the motor on my Vpi Classic 4 to the new SOTA motor which has a different pulley so the optimal length was not known. I have an Origin Live belt which is pretty good but it has a small amount of width variation. I’m not sure if that is a factor in the measurements I’m seeing. Complicating matters is that I specified too long a belt so I cut it down and spliced it several times with super glue until it stopped slipping on the pulley and gave good measurements. But through this experimentation I’ve determined a length which is yielding 45.00 rpm, +- .01%, .1% w/f, as measured by Platter Speed, which is slightly better than what I could get with a VPI round belt. So now that I know the exact length I need, I’m wondering if I can do any better. A Basis site I was reading was describing how they have achieved an ultra precision ground flat belt and how it makes a big difference, but that’s for their own tables. I will be speaking with Origin Live next week. Maybe all I need to do is re-order their belt since I now know what length I need.
You know OP if you like to tinker.. there are a LOT of materials used for making gaskets. All types of natural rubbers, and synthetics. I have made a slough of different O Rings. Look in Granger, places like that..
Haz mat material handling, uses some really cool materials too.

Thanks, you reminded me that I need to give Christian at SOTA my dimensions again. He has a belt and it may or may not fit.
I should have added, I replaced a new Townshend belt with an Origin Live belt on my Rock 7 and the difference was not subtle. I remarked then it was a 30% increase in SQ.
These SOTA motor upgrades are designed for VPI tt’s. I have the motor/Condor/Tach for my Classic 3, came with a belt.

I'd imagine your Classic 4....the motor pulley distance is the same as my Classic 3.
I doubt the Origin Live belt is causing your variations, unless your splicings are crude. I would order a new belt that has the right size, they are not crazy expensive and work very well. I have used them for years now, and even with my current large motor/100lbs platter they work perfectly. The RoadRunner shows speed variations of only +/- 0,003
If you know your exact dimensions, go to turntablebasics.com. Don't worry about the low prices.
Good info, thanks everyone. My Roadrunner is showing about the same variance, so I’m going to pat myself on the back for my superglue job!