ORIGINAL: Montague
Don't sweat it. The fuel doesn't actually flow to the front of the tank in a dive, at least not in the fairly short dives you get in RC flight. Sounds like your tank is set up correctly.
In fact, having the klunk get stuck at the front of the tank is actually a common problem.
I third that. I just spent 10 hours "tweaking" my engine because it wouldn't stay running. I swore up and down that gremlins were messing with my engine when I wasn't around. Turned out that a rather hard landing caused the clunk to get stuck at the top-front of the tank, causing it to draw air instead of fuel. A slight tap against the tank with my foot (
)got the clunk unstuck.