I have the same tractor (M7040SUD) with the 1153 loader. I have used it hard and I have not experienced any weld issues. I'm actually very impressed with the strength of the FEL.
If the OP is serious about his issue, it would be very obvious to a dealer if it was a defect in workmanship or some sort of abuse. I'd imagine the FEL would be bent somewhere if it were abuse.
What I'm really puzzled by, if you bought a 30k plus tractor that has an obvious warranty issue, why are you having your "body man" buddy fix it? That will, no doubt, void the warranty and probably not fix the issue. I never post anything to start an argument (really, check my posts), but this whole thing sounds made up.