I am getting ready to move the boat to a nice heated garage over the winter. I decided that I would attach the keels after decking the boat to make it easier to work on the interior. That has the additional benefit of  making the cradle much easier to built.

The bottoms are 2×12 – 4ft
The sides 2×8 – 8ft
4 metal corner brackets hold it together.

I used frames 3 1/2 and 7 + 15mm offset to get the profile for the bunkers.