[joedoh]

one time I was setting up a back half (cut a frame off at the cab and was welding on a new rear frame section. I put 8 tacks, 2 on each vertical joint, between the old frame and the new section which were butted together. A buddy saw it and said "man I wouldnt want that falling on me when those tacks break" and I just stepped up and stood on the very end of the frame. the 8 tacks held the frame section and my hefty self, even with the torque of standing at the end.

in my case and in the case of those nuts, the direction of force is perpendicular to the direction of weld, so they should be good. if for example, the bolt was left loose and a sledge hammer hit the bolt head, that would be force in the direction the weld and it would be weaker. Since all you are doing with the tacks is resisting the turn, the eventual clamping force of the bolt will be stronger. said another way, you dont need to put 8k lbs of twist into a bolt and nut with a pair of wrenches for it to have 8k lbs of holding force.

welding all the way around I would worry about warping the nut and unintentionally making it a locking fastener. Just my two cents as an engineer and a hobby welder.