[Stripit]

I'm looking at a 2014 Forest River FLAGSTAFF CLASSIC SUPER LITE 8528RKWS. The seller states the GVWR as 8950, Dry as 7513 and liquid capacities of 76 gallon grey, 40 gallon black, 43 gallon fresh water and 60lbs propane.

Well it would be normally unlikely that you would head off into the parking spot carrying full tanks of grey and black. You would start with a full tank of fresh, and by the looks of it be able to then dump that 43 gallons into the empty grey and black tanks. Depending on the situation where you might be able to dump the grey tank on the ground you would end up with a full 40 gallons of black. But I have been wrong many times in the past and this could be another?
Using the GVWR minus the empty guestimated weight less a full tank of fresh water would leave you with just about 1,000 lbs left to add clothes, food, camping gear, hitch and what ever else you put into the trailer. I would start first, go get it weighed before you put a tube of tooth paste inside and see what you really have to work with. Then we can talk real numbers and not be guessing. Just my opinion