I don't think "strong enough" is the issue. Its only strong enough if done properly. Anyone can go out and buy a $200 mig at Harbor Freight and slap down a "good looking" mig bead. Having one done so its "strong enough" is a different thing altogether. By requiring tig welds you've just cut down the number of do-it-youselfers tremendously and a poor tig weld will be much easier to spot.