"How to do this" (12-bolt rims w/ the alignment hole)
1. Put the tires in the sun and let them bake so they are more pliable.
2. Take the tire and figure out which side you want the outside to be. If it's NOT the side with the paint marking, then find the side with the paint and transfer the white dot to the other side.
3. Take the outer rim section, align the 'extra' hole with the white dot, mark where the air valve goes. (You will need this to align the hole on the PVC insert!)
4. Get your tire soap, soap up the outside and edges of the PVC insert. Soap the bead front, side, inside.
5. Set the PVC insert down on the ground on it's side (I suggest a towel or blanket due to the tire soap). Pick up the tire and either 'drop it' or set it on the PVC insert. Now the tricky bit, crawl onto the tire, balance carefully and BOUNCE until the PVC insert is aligned in the middle of the tire.
6. set the tire up on it's side, and spin the PVC insert into place. You need to align the hole with where you aligned the air valve! You may need to push the PVC insert into the tire, grab it and try to rotate it.
7. Center the PVC insert into the bead/tire. (This may be harder then it sounds, but a combination of small pry bar/tire spoon and your foot should be able to do it.)
.... now just follow the instructions from the TM on mounting it to the rim. I would suggest getting 12 - 1/2-20 grade 8 nuts along with a grade 8 1/2" washers. Use those the first time to seat everything down (and torque to spec.). Then you can air it up, verify it's not leaking. Assuming it's not leaking pull the schrader valve, remove ALL of the air.. and then swap the regular nut/washer one at a time for the proper lock-nut. (Follow the torque pattern.)
But I was able to get all 4 PVC inserts in place, and the one wheel installed with the temporary (not) lock nuts. I'll swap to the lock nuts tomorrow after I verify it's not leaking air.
Took me about 10-15 minutes per tire to install the PVC inserts using this method. (Took an hour, w/o an air tool, to torque down the wheel without lock nuts.)