Larry,
I am not an engineer. You ever need someone to find a bar ditch in a reseviour, call me. I got a PhD in that.
RE: Art-
Larry, Everyone has a price, how much salsa ya got ?
Art needs to chime in.
Folks here use the "Z" made from RR track as well.
Logging chains and chain link fence smooth out, you need rocks moved and a crown.
I'd just take Sadie to some RR track getting place and have Sadie just say to the nice man " I want those" and with her charm, the folks will load the things up or deliver them to you.
"kink you" get us, them me , we...everytime.
Then all you have to do is get Art's take on the thing.
Umm, maybe invite the right folks along with LEO and Firefighters out to your place to play with the blackpowder cannon would work.
Smoke got any ideas or sources on materials?
Later-
Steve