Thanks Kevin, I already love it!
Just trying to keep things simple for now. I'm not worried about the tank expanding/contracting as this is not a pressurized fuel system. The only pressure the tank gets is from the muffler, which isn't enough to expand the fuel tank significantly. I'll be checking it before each flight, as soon as I see any problems I will deal with them.
I'm off to go fly it this morning, I'll let you know how it goes.