As was mentioned, the Felt frame is not designed as a gas tank. It us not sealed, and may not be sealable. I believe that the place where you would have to cut the hole and weld a filler neck may be double walled. I watched a video of a so called expert builder have all kinds of problems trying to convert a Felt fake gas tank into a real one. Even if you are successful, you would have top repaint the frame because of the welding. No doubt the Felt frame is better quality than the Skyhawk frame, but I don't believe it is really suitable for a gas tank. I'm considering a more conventional build using a Felt Bixby frame. They are all made in China, but Felt frames are most likely higher quality than the Skyhawk. Everything made by Skyhawk seems to be about the same quality as a cheap Chinese scooter. My last Trek mountain bike was made in China, but in to Trek's specifications. It held up very well.