Here's My $.02-
In January I bought a used 20'+ Beavertail gooseneck trailer, 14,000 GVW. I had to weigh it to get plates. The scale at Metamora Grain weighed it at 5,500 lbs. So, 2 M's, at approximatley 5,500 lbs a piece, (that is what Mine weighed) equals 16,500 + chains, etc. Yes, you'll have pin weight on the truck. Make sure it is rated for the 2-3,000 pin weight you'll wind up with.
(After reading this statement, I believe it may be too conservative, but you get the point.) Which, even though it may take it, My rig wouldn't be legal doing it. ('97 K2500, 8,600 gvw, 6.5 diesel.) All in all, could you do it? Yes. Could you get away with it? Most likely. I don't believe it would be legal, though. The way I see it, the unhooked trailer, sitting on a scale with the tractors on it, would weigh 16,500, 2,500 more than trailer is rated for, therefore illegal. You need to consult a d.o.t. officer, or ask you local police department to get an actual copy (and interpretation) of the rules you'll be dealing with. I think about this stuff, as the d.o.t. in Michigan is pulling over private guys occasionally, and you had better comply, just like motor carriers. I've heard stories.
I figure, the max load for my setup, is about 9,000 lbs. Or, basically, my 7,400 lb Farmall 450D. Or my 2 Super C's. I think you get my point.
Good luck. -Andy