Doug, here's how my set-up is installed under my dash:
Simple angled bracket mounts to the firewall crossmember and then curls around one of the dash-to-trans-tunnel supports. And a simple routing of the pull cable loops cleanly under the car to the 5lb bottle in the trunk.
And here's how it looks from a higher, more normal view:
Flash pictures bring out all the ugly...you can't even see the bracket during the light of day.
-Dean