Absolutely!I think your 12% tongue weight and loading calculations for the 19' are supported by the real world weights of most trailers, however it is possible to have a 2nd gen 19' on the road at under 3500 lbs...
Keeping the tongue weight down this much, and doing it right like Michael, takes care. For a 19', that probably means at minimum passing up the front storage box and dual 6V batteries as Michael did.
Hitch weight limit, tongue weight fraction, optional equipment, and stuff carried in the trailer are all important factors, even in this example of this one chain of limiting factors (and there are the other limits as well). It is each trailer owner's responsibility to make those decisions to suit their situation.