Aschinder - we'll have to agree to disagree.
I feel that the majority of the load on the diff brackets is rotational around the 4 axle bolts & since it is a rectangular piece welded in, the welds will not be seeing much strain.
Side loads will be virtually nonexistent since the brackets only locate the center section. If there was any significant side loading, there would have had to be some form of offset mounting to the frame in the stock configuration (& they wouldn't have the rubber bushings). Picture standing a book on end - it's easy to knock it over. Now open the cover slightly to spread out the 'mounting' points transverse to the direction of the force being applied - it's much harder to knock it over.
There's some merit in what you're saying about the vertical welds - but not in this application. These brackets as you stated are isolated from the suspension so will not be seeing any of the road induced shock. There will be some but it's just forces from the weight of the pumpkin. The welds are plenty strong to handle that.
After saying all that - I'm an Electronics Engineer, not a Mechanical Engineer but I've had some experience in mounting weapon systems to vehicles in the past and more recently a cantelevered Ground Penetrating Radar system to vehicles. I'm not pulling this 'out my arse' for the sake of argument.
One comment that you made that I have to agree with 100% is that if you have done this modification and decide to sell your vehicle - a signed declaration & waiver is a very good idea.
Trust me - I thought this through quite a bit before I jumped in with both feet. I didn't do it just because Zeus said I should. At the rate I was eating CV boots - the risk was well worth the benefit.
Tom
"Even the "pro" didn't have the gonads to mimic my skills!" Don't go there Dude. 'Welder Guy' is sensitive to comments like that.