Turn that tank 1/4 turn and have it mount on the widest side. I think they feed better, metal or plastic, when the fuel load and pick up is as close to the center as practical. Most modern profile designs have room to mount this way. Make a ply wood or light metal mounting piece to glue the tank to, with slots on each end to allow for up and down movement. Attach the tray to the fuselage with those threaded inserts. While the tank is still new, attach the tank to the tray with silicone adhesive. If you need to change the tank you can work it off with a putty knife. Makes for a nice clean installation. You can also hold the tank to the tray with a couple of zip ties also. I'm sure this has been covered before and photos are on the forums somewhere.
Type at you later,
Dan McEntee
If using metal straps, make absolutely certain that there are no sharp edges or burrs on the strip that can work through the tank when the engine is running. It would take as long as you think to do that.