We have deep-water-started riding 2 up on X2, B1, and HX. Myself (180 lbs) and either randy or Ryan (180-200lbs). The hardest was the Hx because the seat was high and it doesn't have that low end snap to pull you out of the hole. The B1 was unstable but it pulled right up onto plane. Naturally we couldn't stop.
My Wife and I ride 2 up on the SJ, SXR and X2.
X2 with pontoons and tall seat is like being on a 750ss. My wife and I could stop in calm water but it would be sketch. I think we could stop on the B1 but we haven't had access to one since I met her.