The frame might survive, but I'd be concerned about whether the spring rate, axles and spindles are beefy enough to carry the weight. There's nothing worse than having a failure on the road fully loaded. Check with a local trailer parts place for details. Compare the weight of 2 jet skis vs. 2 big bikes before much money is spent.
Y0u are right the couple that have responded the gross weight was 1500 lbs. I think I need a minimal of 2000 to be safe with 2 bikes, the Valk or a RSTD and a Fatboy