Are they shorter than the stock rubber mounts? They look like it.
If so, I guess my question is this - and forgive the stupidity of same, I've not eaten my lunch yet, could affect my thinking... - wouldn't that allow a little more damper shaft movement (on a lowered car)? I mean, not a lot, those rubber donuts are what, 1/2" or 5/8" thick? But that's decent travel at the wheel. Could you get away with a thin urethane piece there, on the bottom side?
Maybe I'm smokin' dope....