If your trailer is similar to mine, you can run your RZR as far to the rear as you'd like. But like you stated, you'll want to run it across the scales to know for sure.
I have an 8.5x20 enclosed I use to haul my RZR and Harley. First thing I did before putting anything else in it was load my RZR and run it across the CAT scales. I wanted to know worst case scenario. So, I tied the RZR down within about a foot of the rear door. It handled great on the way to the scales and scaled out to 9.7% tongue weight. At that point, I knew I was golden and I could put my RZR anywhere I wanted. After filling up all of the cabinets/storage, adding a refrigerator, microwave oven, pots/pans, toolbox, etc., there's more than enough tongue weight.
I have an 8.5x20 enclosed I use to haul my RZR and Harley. First thing I did before putting anything else in it was load my RZR and run it across the CAT scales. I wanted to know worst case scenario. So, I tied the RZR down within about a foot of the rear door. It handled great on the way to the scales and scaled out to 9.7% tongue weight. At that point, I knew I was golden and I could put my RZR anywhere I wanted. After filling up all of the cabinets/storage, adding a refrigerator, microwave oven, pots/pans, toolbox, etc., there's more than enough tongue weight.