In addition I also finish welded the seams inside the LCA pocket and the entire K-member. Overkill? Maybe. But it couldn't hurt.
You can see the string of itty-bitty spot welds that were originally used to join the upper and lower halves of the K-member here. Running the bead along both sides really made the assembly into a very solid unit.
I had to roll the subframe over a few times while doing all this work the difference in the stiffness of the assembly was very noticeable. Early in the process I could feel the thing wobble around a bit if I grabbed it by one corner and shook. I mean it felt like grabbing one corner of a sheet of 3/4 plywood. Strong, yet with some springiness to it. With everything welded up it is completely rigid. More like a sheet of 1-1/8 subfloor.
Yeah, my welds still kinda suck and the flux-core wire is messy, but they got better through the process and functionally the welds are good.
Next step.......
Installing the ATS coilover conversion system.......