Explain this concept to a Cujun!

[David Bienvenu]

I have my 66 Seacraft bow rider at a fiberglass shop for a new transom. The top cap was taken off and I pointed out that the front-top of the cap was soft when I stood on it while cleaning my new purchase last month. The cap was turned upside down and cut the inner fiberglass liner out. I expected to find rotted plywood between the fiberglass. Instead there is 100's of 3" x 3" x 7/16" thick pieces of wood layed out end to end. Why is this like this? What should I go back with? I didn't have my camera with me this morning and will go back and take pictures.

Also while the cap is upside down- the copper fuel line that is fiberglassed under the port side of the cap from the stern to the dry storage area needs to be changed. Should I go back with copper, 90/10 CuproNickel,stainless or rubber hose? I'm in the heat exchanger retube business and have all the above in 3/8" OD.