Great pics showing how it all goes together, nice work. Perhaps needs to get a link in the FAQ thread.
Yeah, where did you get that idea for lining a tire with another tire? Some dog tell you, or did you get the same good idea? It really works good, especially with old slick tires. You get some thickness on the sidewall, if pinch flats have been a prob. I like the strip door used for a liner, that is some thick, tough, but flexible stuff.
Personally, I have steered away from pre filled slime tubes in favor of the much chunkier 4x4 slime. Then you have the problem of finding a tube with a stem fat enough to get the chunks into the tube. I have to deal with mesqite thorns more than an inch long everywhere.
Of my 6 ebikes, only one has rear motor and rear battery. It's barely tolerable with a 15 pound pingbattery back there. For a short ride, it's ok with a much lighter 8 pounds of lipo back there. The battery back there, the motor back there, and panniers with heavy stuff would be a pretty twitchy ride. Fine when everything is fine, but when the poop hits the fan, you are going down.