You are talking a 5th wheel and a bumper pull on dry roads. Its doable but like you said don't try to set a speed record.
2 bumper pulls on slick icy winter roads = no bueno.
I think you'd be much better off with a single 4 place
2 bumper pulls on slick icy winter roads = no bueno.
I think you'd be much better off with a single 4 place