Congrats! That tunnel should be quick.

I don't know how if you're aware of this, but that hull is similar to a CP tunnel. CP tunnels have a reputation of being sketchy on shutdown. A lot of CP tunnels that I've seen on the forums have extensions on the outside of the front of the tunnels. I think CP actually built these extensions into the mold.
Here's a link that I found about it.
http://www.performanceboats.com/jet-boats/89570-texas-tunnel-resurrection.htmlPeople make these tunnels work, just with a little modification
Don't mean to mean to be a downer, just wanted to make sure your aware that's all.
Good luck with the build.