Leaking bulkead solution?

[Dreadful]

Alright, so I'm still somewhat of a novice here.. but I tried something most people wouldnt and thats building my own custom sized aquarium.

Learned a lot since I started the project and I finally filled the thing up the other night and I fear there may have been a slight but crucial mistake during construction.

One of the bulkheads leaked a bit. I'm not sure if it was how I had the thing tightened down or if the hole drilled may be a bit too big. If I push the bulkhead all the way to one side as far as possible you CAN slightly see the hole that has been drilled. Also, underneith the plywood isn't exactly flat its all chipped.. but I dont see how that would be a problem

That being said.. IF this is the issue how can I fix short of draining the whole 100G display tank and disassembling and getting a whole new peice of glass..

I KNOW I cant just silicone it as it wont adhere properly to the bulkhead.

Here's what I'm thinking:
If I can cut a small square of some type of material (which the silicone WILL adhere to) larger than the hole and then drill out the proper sized hole in that.. then silicone the tits out of that against the glass.. then install the bulkhead normally over that peice.

Thoughts?