Are you refering to drilling from the tower foot into the boat for your cubby area? I did this on my boat and i drilled from the inside threw the boat into the center of the front foot on my tower.

Mine has a plate on the inside, heavly reinforced with a 1inch fiberglass or some material, then the hull, and the tower front foot is bolted right at that spot. It also has a pre cut hole in the center of all the mounting bolts in that plate. Id post some pics but im not at home this week. I might have some old pics of my amps and how i wired the tower.

If this is the place you are talking about then yes you can drill threw it. I ran my drill in reverse the whole way threw it though. Drilling in forward from the back will absolutly thrash the gell coating. Think of what a drill bit does when you drill threw wood on the back side. It generaly blows out.

I measured a ton of times. Then i took a very small bit and drilled a pilot whole in forward, it was a very very small bit, i wanted to double check my drill location so if i missed my tower leg i only had a tiny hole to fix. Then i progressivly got bigger and bigger till i reaced a 1/2 hole.

The hardest part of drilling threw the bottom of the boat up into the tower leg is the angle. You have to drill it straight up or you realy risk missing the tower foot. This area of the boat is incredably thick. Once i fished the live threw there and pulled speaker wire it was a long task. The speaker wire didnt want to make the bend into the hole i drilled and it took a lont time. I finaly got it and it created a truly seamly wire effect that matched the factory side for the nav light on the top of the tower.

If you have questions ro want to see some pics Pm me