Hi out there!
Here are some requested information regarding the two belts that are used on the tractor:
I use Roulunds Roflex-Graden(tm) belt.
4L 910 – corresponding to a belt with 910/10 * 25.4 mm = 2311 mm
(Actually – I have not used it yet. Still using an old one “before my time”)
Hope this is useful for you!