Cold Hardy Cycads

[Paul Ont]

Okay, if we all agree that Cycad panzhihuaensis is the hardiest Cycad (I know people growing it in both Maryland and D.C. unprotcted, survival of at least -18C has been reported...), how do some of the South African species compare?
Specifically, some of the Encephalartos... Looking at the range maps, and reading some of the altitude information, it seems that a few of the species would likely experience farily regualr snow and temps (probably at least occasioanlly) down to -15C or more!
Anyone have experience with E. eugene-maraisii, E. lanatus, and E. friderici-guilielmii? I would suspect that these would have great horticultural value in zone 8 and probably even dry zone 7's...