[QUOTE=SALLYCAPP;3957404]Progress!. I won the battle.

The upshot is that I got them installed today! I used a combination of approaches. I jacked up the opposing suspension a lot to lower the other side; I also used large C-clamps and a small bottle jack to compress the Sumo Spring on the problem side. That combo gave me enough clearance to get the spring under the iron propane line, and I could drill the first hole. Once that hole was drilled, I secured the upper bracket and then...