"The proper way, and Seatex does this if you watch the video , is to use other materials than just carbon. Carbon is stiff, carbon is light but carbon sucks for impact resistance. There's a way to make a composite box that will withstand windfoil loads. "

One method I use is to lay 'Formica' in among the carbon layers on the box sides.
Light and stiff material and off-cuts available at the local Joinery shop.