Using silicone not silicone grease like mentioned above in a bead all the way around the hole and then seating the bulkhead before the silicone dries has worked for me in the past. The gasket that comes with the bulkhead does not bond to the glass or the bulkhead and it still works fine. The silicone does not need to "bond" to work like this. The silicone fills in the imperfections of the glass and essentially makes a custom gasket. Not ideal and I too would use this as a last resort, only if the bulkhead could not be reversed and of course check, check, and recheck, for leaks.