You likely have a float valve issue as a root cause of the whole thing.

First, pick up the back end of the mower and drop it from about a 3" height a few times. This usually jars the float loose. Now dump about 3 or 4 ounces of Marvel Mystery Oil in the fuel. Give it a good run and see if it has stopped leaking. Use the MMO in your 2-cycle mix can every fill-up. It's a good idea to put a fuel cut-off in the rubber fuel line to the carb and use it after every run. Also, be sure to add some Sta-Bil fuel stabilizer/cleaner to your mix, about 1 oz to 2 gal.
Oh, yeah, the 'gasket' for the exhaust transfer pipe cover under the mower is of no concern and has no function. The box protects the exhaust transfer pipe (from cylinder to above-deck muffler) and the box cover is for access to the pipe.

Thanks for the tips. I just wasn't thinking the problem wasn't even related to the gasket.

Heh heh , you're preaching to the choir Saxman. My old LB was leaking past the needle valve, until I discovered the factory fuel shut off. I have been using your regimen of adding MMO since I acquired the 7072 6 yrs ago, I've have done nothing to the engine but rinse out the foam air cleaner, every once in a while.