The Racing organizations will accept 2" belts now that were once used for Juniors and that acceptance is based on changes to SF16.1 16.5 16.6. The 3" belts are still acceptable.
https://racer.com/2019/04/09/how-two...ed-the-system/
https://www.sfifoundation.com/wp-con...6.6_042018.pdf
https://www.sfifoundation.com/wp-con...6.1_022614.pdf
https://www.sfifoundation.com/wp-con...6.5_122914.pdf
So basically all three specs allow widths of 1.72" min - 3.10" max.