I'm not using Z-wave dimmers with the LR6s yet, but I have a house full of LR6s (~60) running on Lightolier Compose dimmers (X10 variant) without issues. The lights dim to about 20% before turning off. The Compose dimmers are all 3-wire (requiring a neutral) and they are rated for incandescent and magnetic low voltage transformers. If I were going to try Z-wave with the LR6, I think I would stick with a 3-wire dimmer such as this Leviton:
I haven't actually tested this combination though so if you buy one, make sure your retailer will take it back in case it doesn't work as expected. Please do post your findings if/when you locate a Z-wave dimmer that works well with the LR6s.