I would say try it!
I ride two ip every day. I find the bike really only fails a bit on open highway 70mph when you hit a long hill and your forced to 4th gear. Or to open to full throttle. But tbh you kinda have to do that 1 up a lot of the time here in uk as its all hills where I live lol. It's a great bike two up. Ok so it's no t-bird but What have you got to lose?
We travel with me(19st) and the mrs (12st), a tent, 2 bags, a case of clothes, stove, food, and feck knows what else. Engine couldn't give a crap most of the time.
Only thing I would definitely do is change the shocks on the rear to something like the hagon 440 if you haven't already. The stock shocks will ruin your experience very quickly with the constant bottoming out on crappy roads with two people on the bike.
