I've had up to four people (under 600 lbs total) onboard my TI with no significant performance issues (two in the seats and two on the tramps). However, due to the capacity sticker I've been turned back to shore by local police water patrols.
I resolved this problem by covering the entire deck with Hydro-Turf, including the sticker. I haven't had a problem since. However, I do this at my own risk and would never recommended it to anyone else.
In 1973 the US Coast Guard effected a regulation, Title 33, Code of Federal Regulation, Section 183, requiring all monohull boats under 20 ft to carry a plate posting the Maximum Weight Capacity, Maximum Persons Capacity and Maximum Horsepower Ratings. However, sailboats, canoes, kayaks, and inflatable boats are
not required to include a capacity plate.
So the TI is not required to have the sticker, but since Hobie includes one it is technically not permitted to remove it or cover it up. This is a real Catch 22 and can be very frustrating to someone who wants to safely use the TI with more than one passenger.
By including a sticker that clearly permits only two people onboard, Hobie inadvertently causes many people serious issues with legally carrying more than one passenger, yet they inexplicably show up to five people onboard the TI in many of their own advertisements which makes no sense.
(Hobie TI Gallery Photo)
So they may be violating their own sticker and technically may be at odds with Coast Guard regulations depending upon the interpretation.
You'll need to decide what you want to do. If you buy a TI and wish to carry more than one passenger you also may technically be in violation. This may or may not cause you issues depending upon how your local law enforcement officials interpret the sticker. The sticker says 2 Passengers
or 600 lbs which is somewhat ambiguous. It's up to the law enforcement agency that inspects you as to exactly how this is applied. They may have a policy or it may be up to the individual officer that inspects your boat.