Overflow Kit installation Questions

[bigbabich]

I have a predrilled 55g tank and I'm installing the Megaflow Overflow Accessory Kit.
ANYWAY...the bulkhead seal that screws in under the tank doesn't fit as part of the tank stand is in the way.
Is it OK to just glue the bulkhead adapter on the top side of the glass and not use the seal on the bottom?

Also, what should I use to seal the pvp pipes? Should I use anything?

thanks for your help.