The adhesive is some sort of calking. I would pull it off the foam, then CAREFULLY cut or remove the stuff from the board. Don't damage any of the copper strips on the board.
I would use a latex calking material to stick the board to the new plane.
If you used epoxy it would be hard to remove and reuse the board again with out damage. There are some double side foam tape that might work, use a large enough piece to keep the board from rocking back and forth.
There are a lot of planes the 6400 can be used in, check Bob Selman designs.
I want the Micro Triton