Take a look at my member picture library. There are some pictures of the deck extension. Let me know if you still need to see better pictures or need more info. I modified the deck extension by placing a pedestal base to give more room in front of the pedestal. I had posted some details on this forum before. I'll search and see if I can find it.
I too am looking to build a deck extension for my 96' nitro 170DC. I would like to know how it is made and secured and how to attach it to the floor and also put a seat pedestal base in that will be stable. Looked at the pics by Paul P and it looks good. Hope you get yours built and if anyone has any info and details on helping me with my project I would be greatly appreciative.
The deck extension is just press fit into the slot. There is a lip of fiberglass that it sits on. Read my other post mentioned above since it discusses the deck extension pulling out. Placing the pedestal mount toward the front of the extension will help minimize the chance of the extension pulling out. If you use a seat up front then the pedestal offset attachment works nicely.