Any tips on fitting the US Car Tool Sub Frame connectors?

I just finished the initial fit up on my 73 Dart Sport project. I had to do a bit of cutting to clear the e-brake cables on both sides. I also have to reroute the gas lines on the passenger's side. I had to do about 6-8 fit-and-remove on each side to trim off small pieces of each one until I had a decent fit. I also had to split the channel on each side in the rear as they would not fit over the existing frame rail. I used screw-adjustable jack stands on each end to jack them in position. Take your time, cut it a little at a time, and when you're satisfied with the fit, tack each end to hold it in place until you're ready for final weld. To see what I ended up with, check out the last photo in my restoration post: 1973 Dart 340 Sport Project