I never did like the tear drop tank sitting on the frame so i modificated it. Instead of a 1/2 gallon tank its now a gallon tank sitting in a wooden basket in the back. There is room for 2 - one gallon tanks actually.
It's not really gravity fed, but siphon fed. The siphon has never failed, even on hills. I put the tank inside a pillow blanket when im riding so the orange can doesn't show. If there were someway to make the engine invisible i would do that too! I don't like the attention so much.
The fuel line runs down into the tank. I found a bleeder valve at a hobby store and screwed it into the plastic tank so the siphon works properly. Here are some pics.