On the drain pipe thing....I have a way better solution. on my 20, once I pulled the tank I glassed in 1\4" thick material about 12" wide across the very bottom of the belly. This gave it a very wide channel to drain, yet sealed it off from the tank area. There is plenty of room to do this and the tank still fit fine BTW. Go all the way to the cross member where the cabin is and all the way to the rear one just in front of the bilge area.
Like this.
The pipe thing is eventually gonna clog again anyways. This way you can actually get into the cabin and hose it down all the way through the belly to be sure its clean. ;)