You know...the Kelly SHU is now available in a composite/synthetic version at about $50 for the complete setup.
I own the aluminum version, and I can't imagine someone building something as good or clean, that works inside or outside the drum, for close to the same price...assuming your time is worth some money as well.
Looks like a cool device. I may try my hand at fabricating something similar. I actually like tinkering with stuff and the suspension is definitely an improvement over my existing internal mount.