I have been laminating 200g twill carbon onto 5mm plywood recently to make kayak footrests and vacing them using the EL2 epoxy and slow hardener.  Most of the time they come out perfectly and just what the customer wants but every so often the carbon does not bond to the wood in a corner.  I always make sure the wood and carbon are fully saturated and down properly but 1/10 this always happens to and is always on an edge at a corner.

Found that myself, sealing the wood stops the problem.  Make sure your using decent quality ply as sometimes it can lift the surface of the wood.  I found birch ply to be pretty good.

What are you paddling?  In all my botas I've just had foam blocks wedged in.  Nothing as quality as a piece of board!

It's for sprint kayaks, most of the boat is made of composites which makes it a bit nicer to have carbon footrests as well!

www.pandakayaks.co.uk