Hotlanding,

It seems you are OK in your tank set up.

One method that may not seem so attractive, but at least will keep you flying, is to start the engine with the plane sitting inverted in a stand. Once running fine, just flip the plane over one wing and put it down to the ground.

In general I think it is harder (!) to hydrolock an upside down engine. Why? Because fuel tend to drip straight out of the carb rather than down the crank shaft. It seems strange your problem.

One potential cause could be over filling the tank, hence fuel pressures into the carb. A guide line can be to watch the pressure tubing from the muffler. Once that starts to fill it is time to quit running the fuel pump and maybe even reverse it for a second or two.

One other idea right out of the blue: Have you checked your piping to ensure that the line to the carb actually is the line from the clunk? If you mixed those up it could potentially makes strange things to happen.

Well, at least some suggestions to work with. Almost all my planes have more or less inverted installation and they seldom hydro lock. For me it is more usual that I end up trying to start a dry engine.

Anyway, best of luck!

/Fredrik