it's not the welds that aren't safe, it's the mounting point for one. You mounted it to the fender well correct?
the correct way to mount it, would to have it tie into the cars frame rails, or a stronger point. If the car were to flip, instead of the energy being transfered into the strongest points of the car, the energy would transfer into the fender well, which would then buckle under the weight and become crushed. That is of course, if the welds don't break under stress and the thing comes apart. There's a reason why the main hoop is a single peice of steel.
the strut bars look nice, but like someone said earlier, they are MUCH stronger when perfectly straight, and mounted to the plate up at the top.
not really claiming to know anything either. I've never built this kind of stuff. More or less i'm going based of observations of other cars, and my dad's 66 VW. all the mounting points mounted to the strongest points of the pan, and the rear mount went through the body, and bolted to the transmission horns (another major structure point)
The way i kinda think of things for mounting stuff like that, is if i can dent it with a hammer, it's probably not strong enough.