Add a backing board so that your hole finishes clean. Shouldn't matter if you drill it filled or empty as the load will be applied eventually. Make sure that its a "backing board/panel" and not a support piece.
Talking about drilling stand. Whos drilling tanks to hook up FX's thats all the work without finishing the sump job imo.
Talking about drilling stand. Whos drilling tanks to hook up FX's thats all the work without finishing the sump job imo.

