Jeff, nice write up with pics! I do molding on the side as well. I use smooth-on's product line
http://www.smooth-on.com/ They have a good vareity of urethanes, silicones and resins. I mainly use their 300 hard plastic or 326 fexible plastic products. Molding is fun!
I am working on a vent cable sheath right now. But it is tricky because one half needs to be rigid and one half needs to be flexible, but its all one peice! I am using a metal dam in the mold and will pour both the hard side and flexible side at the same time. Then when both are the same level before curing I will pull out the dam and let them mingle in the center
