About 200lbs would be a good ballpark figure.
Just an fyi, a Road Rebel (32) might be a bit much for the Rotax and Mojo’s, unless you’re carrying a lot of weight.
Even the Masters guys tend to run the KT1 (30) or Blackstar (30/32), if they’re on CRG. I personally weigh between 190-200 at racing weight, and run a 30mm Italkart Rapido V. The only 32mm karts I tend to see in Rotax are the OTK karts in Masters at the heavier weights.