I just replaced the rack boots on my midget and it was a real bear. Here is how I did mine. First remove the wheel, take off the tie end set - making sure to not loose the exact position of where it has to be returned to so your wheels won't need to be re-aligned. Next slipped the Rack boot on and on the large end attach 3 very small clamps. I used clamps called hemostats that hospitals use. They lock so they allowed me to grasp them and pull (stretch) the rubber. It took a fair amount of stretching to get it over the large piece of metal but eventually the boot did slip on. The clamps have to be really thin so you don't take up valuable space.
I am sure there are other ways that may be more practical, I just don't know about them. There isn't a lot of space so expect bloody knuckles and when I got totally frustrated I had to walk away and do something else. Just keep trying and eventually it will slip on.
Good luck