A little late in the discussion, but did you fully weld the trailer to the frame? The pics you gave only showed a few beads. If I was to buy a bobbed deuce, I'd want the trailer frame cut at a 45* angle and a plate fishmouthed along the majority of the weld.
As for the frame welding itself, like stated previously, the 4x4ers weld frames all the time without incident properly gusseted.
If this were say, an F350 being lifted, welding a frame on a frame would be considered half assed (not saying your work is at all!). Longer springs, shackles, hangers, or whatnot would be a better route. Why not just do a combo of more springs in the pack, drop hangers, and a longer shackle? I can't imagine the ride or flex is very good at all with TWO spring packs on top of each other which also doesn't sound/look very safe. I'd be a little worried with u bolts that tall as well. Less springs=softer ride/more flex. Longer shackle=softer ride/more flex. How much lift did you go with?
Eventually I'd like some sort of lifted deuce, althought I'd like a 6x6 lifted deuce without stacking frames. Seems like it'd be a PITA though with the suspension design. I haven't looked into it too much yet since I still have to buy a deuce!