Great discussion everyone. I did not realise about the load rules in BC, I have driven through there many times with my existing camper, and never been stopped or had any problems. I see guys towing two trailers in Alberta all the time, seems sketchy.
Towpro, thanks for the links, these were the exact ones I was using! I was coming to same numbers and conclusions but my stumbling block was that when I applied those to the campers I was looking at nothing added up.
Basically, if I still want to haul my bigger trailer (~6500lbs) with camper, I have to get a Northstar Liberty out of Montana since it does not extend past the hitch and I can keep my tongue weight down by not adding extension. Or, I have to give up taking the camper and the big trailer places and get a camper that puts me right on the edge of weight.
This whole ordeal gets less fun the more I look at it.
I wish our good old '78 had a bit more comfort for winter camping and a bathroom and electric jacks....