Well, its that time of year and it means many will be considering purchases of Hi-los and/or tow vehicles. And I do not mean to sound condescending as I have been at this point myself a number of times:
"...and figure a 80% of the GCWR (7600#) for not overloading the tow vehicle is a good calculation or am I missing something. "
Im not sure what you are, exactly, referring to, here. So..... lets just cut to the chase.
You want a trailer that doesn't exceed the capacity of your vehicle as well as the GCVWR with the caveat that the total weight of your tow vehicle is the other variable, here.
You want to know the "hitch weight" of whatever trailer you buy and I believe 15% is sort of the going percentage of what to hope for - as in 15% of the gross weight of your trailer.
But, my trailer hitch weight tends to run heavier.
you want a tow vehicle that can handle the weight of the hitch as well as the weight of the vehicle itself and gear and gas and people etc. That is your GVWR.
I have long ago given up on putting a lot of faith in "published" on capacities and actual weights of trailers and vehicles. The vehicle and trailer weighs what the scale says it weighs. The hitch weight is what the scale says it is. The GVWR of my truck is what the sticker on the door says it is.
Again- if you have owned a trailer/rv before you know this and so I am not trying to be a dink. I just know I have put my hopes in calculations and estimates , before, that I arrived at from applying general theories and published weights and, when all was said and done, the scales told me i was off.
From what I can tell- a 24 ft or bigger Hi-lo will be pushing the borders of what is acceptable for a 1500 size or smaller tow vehicle and even some of the shorter of ones. If you have a 2500 or bigger vehicle- I think most will work. But, in the end, I would weigh it all.
p.s.- that calculator that Ruben posted is a good one.