Just a fun project you guys might dig......

[special fx]

1) I would use 1/2" Divinyacel foam and glass both side for buckheads and decks.

2) An access port/hatch to the actual tunnel area so you can clear out any debris from within the boat. Factory Yamaha jetboats have this...check it out.

 

[The Penguin]

This is the only picture I've found so far - is that what you are referring to?

http://www.groupk.com/yjetboat.htm

Looks like buying some sort of a plug and then glassing a housing on top of the pump tunnel would be the thing to do?

Does your CS have a thick bottom? Mine seems to have about 6" bottom (foam?) between the floor and hull. I can't tell from your pictures. did you glass from the outside and then blend it in on the inside? I'll have to cut out part of my floor to get to the crack in the hull for repair...