Which Air Shocks to buy and how to install them

Last August I installed a U-Haul (Curt) hitch so I could carry my Bike-E recumbent bike and eventually tow a trailer. I bought a Yakima StickUp rack because it was the least expensive one that would carry a relatively long wheelbase bike. Thule and others have similar ones. The first time I took it out at night oncoming drivers flashed their brights at me. Both the hitch and the rack are steel and together weigh much more than the aluminum factory bike rack, which wasn't yet available when I started this project. I tried a second bike and the rear bumper was an inch down. smart 450s have a headlight adjustment knob on the dash to solve this problem. I spent a few hours on Google and found nobody makes taller springs for smarts, just shorter ones. Neither Gabriel nor Monroe had a listing for a smart and their support people just recited what I already knew. I couldn't find air springs small enough for the smart coils which are about 2-3/4" ID. I bought a 4" Test-Ball at a plumbing supply. It is the same shape as an air spring bladder and its Schrader valve would stick down through the bottom spring pad. I squeezed it into the spring but it was too short to raise the car. It is made of soft rubber and probably wouldn't have lasted long in this application. You can see it in one of the attached pictures. I measured one of the standard shock absorbers and searched through the chart of extended and collapsed lengths on the Monroe web site. I found their MA805 to be very close. They fit '53-'62 Corvettes, some AMCs, some Fords and others so they are easy to get. I called Monroe to check the outside diameter, 2-3/4". My favorite auto parts store didn't stock them in Monroe but crossed them to AC Delco. The Delcos were 4" in diameter, far to big to fit. I got Monroes from someone else. They fit but came very close to the seam in the frame. I bent it down with a ball-pein and they then had plenty of clearance. The American style pin and bushings on top work fine as-is. I bought two 1/2" ID x 5/8" OD x 1-1/2 long and two 3/8" ID x 1/2" OD x 1-1/2 long steel bushings at Lowes. They fit inside each other. I drilled the inner ones to 25/64" ID to clear the standard shock bolt. I needed two 3/8" SAE washers on each side of the bushings and the whole thing fit snugly into the stock bottom bracket. The air fitting can only face straight in, which would have hit the frame, or straight out, which was about an inch from the tire. The kit supplied with the shocks has a straight hose nut which would make the hose rub the tire. The Monroe catalog showed a primitive drawing of an air line kit with elbow fittings, AK29, which I ordered and fortunately it worked perfectly. Be careful not to drop and lose the tiny o-rings when you take off the dust caps and install the air lines. Push (by hand) the elbows hard onto the fittings or they will leak. I tied the air lines up in six places by drilling 7/32" holes in the plastic skirts for the Monroe clips. I used a regular fish tape to snake the left hose across as high above the mufffler as I could. I drilled a 23/64" hole in the rear valance for the valve tee.
The first picture shows the shock tower with the original shock removed. The second one shows the frame modified. I really didn't butcher it as badly as it looks in the picture. The third one shows the shock and air lines installed.
I drove a hundred miles on them with no pressure and they are only slightly stiffer than stock. 100lb raises the rear about an inch. I will make a run with my bike on Monday.