We have a 390MP, so the weights will obviously be quite different. We have a washer and dryer in the front closet; fresh water tank was 2/3 full; black and grey tanks empty. No generator installed in the unit.
Advertised pin weight: 2744 lbs (20% of dry weight)
Actual loaded pin weight: 3650 lbs (22% of actual weight)
See attached calculations made from actual CAT scale weights.
So, if you estimate the loaded pin weight as 22% of the max trailer weight, you will have a pretty good estimate. If you want to be more conservative, increase the percentage slightly.
Hope this helps.