@SquirrelTail - Just thought I might chime in with some ideas for the exhaust pipes.
In the spirit of cheap, commonly available materials, what about using cardboard tube (like the middle of a paper towel roll) or perhaps some thin wall PVC pipe (like Schedule 10 or schedule 20 PVC)?
I've read/heard that with careful application of heat you can make PVC pipe pliable enough to form/bend and work with.
Just some ideas.
Really like what you are doing and the build is looking great so far!