I didn't have time to post some pictures of my set up yesterday but here it is. Aluminum is pretty easy to work with. I used a jig saw with metal cutting blade and a big file to shape to fit boat contour and round corners. I have some access to underneath so just placed the aluminum where I wanted it and used a 1/4 x 20 bolt dipped in some boat polish (just as a marker) and came up from underneath using old holes and marked where to drill. I drilled the holes then took a bigger bit to countersink a recess for the head of the bolt to fit in so I had a flush top. Then I oriented the terrova on top where I wanted it, and marked where to drill holes and then drilled and tapped for 1/4 x 20 thread. I then bolted down the aluminum to the boat and used stainless bolts with fender washers and nylock nuts underneath. Then I bolted the terrova to the plate using the 6 holes and 1 inch ss bolts.
Hope this helps others.
HHD
GnawMart Tenderloin Sandwich Prostaff, Gnawbone Indiana