RE: Patriot related
Round backplate mount will fit, but you will have to airframe mount the needle valve (or get an exhaust mounted version). Also engine/spinner/cowl spacing may be a little tricky to adjust.
I do not recommend a hopper tank with a bubble tank. No way to get all of the air out of it. You can configure two bubble tanks in parallel though (yes, it works well).
No need to put the tank on the CG either unless it is just to find some room to install it. Even so, with a bubble tank, you can draw about 25% further than you can with a standard fuel tank.