T-Top on an 18

[toadfish]

I have a 1985 18 footer that I have been refurbishing. I am wanting to install a t-top and a leaning post. The top should be through-bolted through the deck for strength and to prevent water intrusion. Does anyone have any suggestions on how to do this because there is no access other than the inspection port in near the bow and the one over the gas tank. Can anyone give input on how their t-tops are fastened down??? (will screwing them down be strong enough??)