I threw the stock fuel tank away. It's too small that I replaced with a 13oz Dubro tank. I wrapped it with bubble wrap, pushed in the slot, jammed it in place with foams, then install the landing block. This larger volume should make at least 20 minutes of flying at full throttle. My engine is a 46 Evolution 2 stroke with 11x8 prop. It's a pain to install the engine in a tight cut off space. I did not bother to cut the slot bigger. After some struggle, the engine sits in fine.