Fuel tank placement

[lbk]

I have a kb .40 that I put on a ARF trainer that I just built. I can't keep the engine running properly. It is hard to start and once its going, it will run for about 45 seconds then stall. I'm sure its a fuel problem because the engine runs fine when it is bolted to my workbench.

My best theory is that the fuel tank is too low - and the engine can't suck the fuel "up" as far as it needs to. How high/low should the tank be in relation to the engine? Any other suggestions on fising this type of problem?

Thanks.