How to put a tunnel in a flat bottom skiff

I have an 18' flat bottom skiff that is 72" wide at the bottom. I am going to be in some seriously shallow water so I was thinking of putting a tunnel in the bottom and buying a jack plate. Any thoughts on how to construct a tunnel for inexpensive? Thanks

 

No but do tell of what and how it is constructed. Actually, post pictures.

 

Down here at South Padre Island, Tx. we have to operate in the shallowest bay system in the US. Average depth is less than 2 ft.,a lot of it less than 1 ft. Tunnelboats are the norm here, but they are difficult to design correctly. Before you butcher your boat and possibly ruin its performance here are some suggestions that I use to run my nontunnel boat in water as shallow as 4 inches. First, and most important, a good stainless 4 blade supercupped prop. Extreme cupping is essential. Second a jackplate with 6 in. setback, and last but definitely not least is a Bobs Machine transom water pickup. The water pickup can be modified with a stainless livewell screen to keep grass out, very important. With this setup I can run in 4 inches and take off in 12 or less if the bottom is soft and the transom pickup keeps mud and grass out that other low water pickups ingest.