500+ degree rubber? Ok, that's intriguing...you could use something like that to stabilize components, and even the hottest-running ones won't foobar that. That could make it even more useful for using it to "shock-absorb" tubes, which is always an issue when doing high-volume gigs (raves and the like).
Oddly enough, the one PCB holder that I prefer is actually a cheap RatShack POS. For some odd reason, this crummy 3rd hand has never wound up in my "I need to replace this" list...because it works, it's simple, and it does what the box says. Tried the expensive ones, things like edge-clamped stands, etc...nothing worked as smoothly and fit my soldering workflow like that cheap little piece of crap.