RE: Well bugger, I busted a backplate.
I would do the Ebay thing too. If you want to fix it, a countersink from the back side of the backplate, and then a matching boss that would come in from the back would work. It could be JB welded in. Of course you would need a lathe. A flush rivet kind of thing. As was mentioned before, a piece of tubing coming out of the (a) hole would work good too. Make sure to use a short screw on the inside of the tank to hold it on to the crankcase. A bigger tank is always useful. I know a guy ran a Babe(y) Bee with a huge tank like that to set an endurance record with a mouse racer kind of plane years ago. I had the same thing happen to my Baby Bee a long time ago. I don't think I said "Bugger" though.