DIY footboard and pedals

I want to build a new footboard, my plan is to buy a carbon fiber plate and cut it by CNC.
My questions is:
a 5mm plate is strong enough?


Probably with a thickness of 5mm I cannot connect board and pedals with a carbon stick, 


but I have to use steel hinges.

5mm solid CFRP plate will be strong enough, at the same time unnecessary heavy and expensive -> even 0.5mm cfrp plate (which is usually the thickness of lamination consisting of 2 layers of ~200gsm carbon carbon cloth) will be more then enough when used in a sandwich fashion, eq 2 thin cfrp skins and a thick (~10mm) lightweight (foam/honeycomb) core laminated between them - it will be significantly lighter and even stiffer then solid 5mm laminate plate.

What about using a very thin SS rod instead of a carbon stick (say, an old bicycle spoke).

A bicycle spoke looks like a good idea, but I am scared it will soon be rusty

Helldiver a sandwich with honeycomb is too complicated for me to assemble. To cut out a carbon plate looks more simple.  So which thickness do you suggest? the pedals can be thinner (maybe  1 mm? ) and the footboard 3 or 4mm?

I have made my own footplate with pedals for a k1 to replace the tiller setup that it came with. I used baltic birch plywood, 3/8” thick, as that was what the original tiller footplate was made from. I cut out the footplate and pedals and wrapped them in epoxy and glass. The original was just varnished and not glassed, but I wanted to be sure it was bombproof. I used a foodsaver device as a simple vacuum bag. For the hinge mechanism i found some thin brass tubes and rods in the cabinetry section of a local hardware store. The rods fit in tube with incredibly tight tolerance. I filed grooves in the pedals and footplate to set the sections of tube into in a bed of epoxy.   I cut the tube into 5 sections and then the rod ran through all the tubes. Because of the tight tolerance I had to glue all the pieces of tube in place while the rod was inside so they would be lined up perfect.  It works beautifully. The main cost was a $35 sheet of specialty plywood that should be enough for about 12 more footplates. I only have a few random pics of the thing in various stages of assembly.

fyi - the large hole in the middle of the plate was required as it allows one to reach a hand through to access the adjustment hardware that is behind it; would not be needed with a surfski.