Connecting a bulkhead to an EPDM liner

I want this to be done! But this bulkhead is giving me a lot of grief. I get that it was not designed to connect to EPDM, so here's the solution I have come up with.

 I cut a piece of 3/8" plexiglass and applied a lot of silicone to the underside. Then I washed it, and the EPDM with denatured alcohol and applied this fish safe EPDM seam tape.

One thing I've learned is that if the bulkhead is over tightened it will squeeze the soft inside gasket out of round, and cause the seal to fail.  I'm not sure... this might be what happened yesterday, but if this does not work I'm just going to smother the fitting with even more silicon until it complies.

This has turned out to be a lot more difficult than I ever imagined and I'm tired of dealing with it!

UPDATE

I found the source of my leak.  In my attempt to squeeze all the bubbles out of the silicone I literally stood on the acrylic and jumped up and down on it.  Apparently I caused a small crack in the plexiglass, and the leak.  
To view my repair which was done with much more silicon and care click here.

I'm taking no chances.  This hole saw fit over the bulkhead and the two lead weights and a 3 lb hammer will keep the pressure on over night.

I might be overly optimistic, but I have faith, and have begun to shovel gravel into the grow bed.