Fish box thru hull ?

[Capt Chuck]

BUT was wondering if I need to re-enforce between the hull and the liner to create a solid base for screwing it tight withuot flexing the skins too much.

When you get the old thru hull out you will see that the inner liner & the hull are thick enough to support the tightning. I don't think you can get access between them to reinforce anyway. You don't need to torque it down. Use 4200 vs 5200 cause you might have to remove it some day. Like I said just keep a watch over it.

NOTE: You might have to grind down the Gem's outside flange to create a flat section angled so it will fit tight againt the chine. Just dry fit it a few times before you lock it in place.