I don't know of anyone breaking their TI's in or around the AKA cross bar mounting points (at least no one has mentioned it on the forum that I have seen). Though I suspect we are not supposed to, we and others have had quite a bit of weight on our TI's on many occasions. The label on the trampolines I think says max weight 200 lbs (90 kg) each tramp. I weigh over 100 kg and if I jump on an AMA it doesn't sink completely, so I assume each AMA's boyancy is around 250 lbs (113kg).
In the US the plaque on the hull is printed max 2 occupents 600 lbs (272kg), but I'm pretty sure that is for the Kayak hull only (without the AMA's) since they can be used separately. It would be nice if Hobie had two plaques, one for Kayak only mode, then another for AI mode, (I suspect they are only legally required to plaque the kayak hull itself). Perhaps they can clarify for us, or maybe it's better not to. I interpret the loading to be 600 lbs and two occupants for the Kayak, (this compares to some of their other boats (like the Oasis for example)). I then interpret the Tramp loading (200 lbs each) on top of the Kayak only loading, at least that's what I will be telling the CG (as they are hauling me away, ( in a whiny voice)), I'm just hoping they don't Taze me, (has to be a whole lot worse when your wet LOL).
My wife and I have taken our TI out several times now with her 200 lbs (90kg), and me 220 lbs (100kg), plus 4 scuba tanks lashed to the AKA's (30 lbs(13.5), ea), plus all of our BC's weight belts, fins, spear guns, coolers, beer, etc (another 100 lbs(45kg) for a total weight of 640 lbs(290kg), we have made many long runs (5-15 miles one way) in sometimes fairly rough open water and 15 mph+ winds) with no problems (mostly down in and around Key West, FL). On light days we have gone out snorkeling with 4 adults on board (two in seats and one on each tramp), about 800 lbs(360kg) loading with no issues, except the rear seat passenger is sitting in water (like on an AI), other than that the boat handles fine. But we tend to stay in shallow fairly flat water (just off Higgs beach in Key West). I wouldn't feel comfortable going out in open ocean with 15mph plus winds and 2-3 ft seas loaded down that much. I always carry 6 PFD's on board.
I'm not suggesting anyone do what I am doing, but I'm on my 3rd TI now with way over 2000 sailing miles on TI's with no major issues besides the normal wear and tear (broken rudders, AKA sheer pins, front AKA weld joint, etc), which I have had my fair share of. But then again we use the heck out of our TI's and just love them (perfect boat for us (living in Florida)).
Here is a link to one of the best video posts ever from Stringy showing a loaded TI, perhaps this will set your mind at ease ( viewtopic.php?f=70&t=38060&p=154879#p154879
Thanks again Stringy, this is still my all time favorite TI Video.
Like Tonystott is saying though, you might have a defective hull with a thin spot, that should be checked out.