I did the same and was greatly surprized at the difference. Was really impressed with the cruise no drone at all. Idle is simply terriffic let alone acceleration. I think you made a wise choice. I went one step further and installed a Callaway Honker CAI system. My baby just goes. Good Drives my friend.
My tips are even if you look at them from level behind. However, if you get elevated and look down on them from the rear of the car the center tips are farther to the front than the outer tips.
When I tried to adjust for that, the tips were straight from above but canted from the center downward to the outside when looked at from behind. I banged my head for nearly 2 hours trying to make them even both ways. I just left them even as looking from behind and haven't worried about them since.
A nifty tip for alignment that I saw was to put a short length of 1x4 across the top of the tips and use spring loaded clamps to hold the tips even while tightening. However, I don't know if it helps with the front to rear alignment.
I and my mechanic banged as you did with little luck They still look great but if youlook down you cna see the difference.. He suggested spot welding a bar as you mentioned. I was wondering if any of these aftermarket plates/dividers that go between the two would pull them into alignment.. Most say for factory only but