Test fit of the base on the blank. I used a washer to give me a 1/4" edge around base. I picked this up from an article on installing a window in a computer case. Place the washer against the edge of the base and then use a pencil to draw around the edge.
I used a washer that I am using when I actually bolt the bases in.

I used a jigsaw to cut the 45 degree angle I am using on the bases. This should allow the carpet to lay better.)

If you zoom in you can see 2 of the dots I used for drilling the holes. I used a black shrapie pen and held it as straight and in the middle of the hole in the base as I could and just touched the wood.

I used a 3/8 inch spade bit to do the holes. I also used a scrap piece of plywood under the drill so I would not tear up the bottom of the wood. (sorry lost that picture the T-nuts are installed here)

The T-nuts are installed on bottom. I used a hammer to tap them in. You can also use the nut and a washer and draw them into the wood slowly.

Notice the T-nuts from the top? You should not see the top of the nut or your wood is too thin.

I am placing the seating base that I made previously for the boat.
I am duct taping them so they don't move.

I first determined the spacing from the dash so as to give people some room to move.

I placed both seats on the bases and moved them back and forth and swilveled. This helped with spacing and clearance for sides.

I mixed up my epoxy and glass fibers only till it was fairly stiff.
I smeared a small amout in the middle of the base. The duct tape was used to make a hinge and allow me to adjust the bases.
The rocks are just helping me keep them down on the floor.
in 24 hrs I might test the seating but really need 48 to be sure they are glued permanently.

They work just fine we went out and had some great fun but removed the seats to install the carpet. On inspection there are no cracks or any sign that this will not hold up and we did some wild waves. More pictures soon!

Much to my surprise and delight the edistal mounts do not show up and you can hardly tell they are not directly mounted to floor.

The mound was cut at a 45 degree angle and glued directly to the floor with 6 T-nuts installed. I had to cut the carpet under the Bases to find the nuts but it worked out better than I had hoped!