You would repair them like any other board, they are the same underneath.
However if you need to repair a crack underneath, you will have to cut the skin away from the area first .

You may be lucky and be able to cut a section of the skin off in one piece, then you can save the piece and reattach it after you have done your repairs, but more than likely it will all break off in tiny bits so will leave you with a horrible looking section.

I did a small repair on a Starboard GO after the extension dislodged from the uni & the pin went through the board. I cut a cross-shape in the eva and wit a sharp chisel, peeled it back. Glassed up the ding, sealed it & stuck the deck back down with contact glue - faster & easier than a paint repair job!

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