First, the clunk doesn't need to reach the front of the tank, nor do you want it to as it will sometimes stick there. When you are in a dive, unless it is a dead stick dive, you are going to be dropping faster than the pull of gravity. IE 16 ft per second per second. The fuel is going to be like anything else, and floating or pinned to the apparent top of the tank. Static test, IE holding the nose down should result in a dead engine if held long enough. That is not going to happen in the air though.

Don