Hi! Welcome to the fourm. Unfortuantely, I dont think you can do that with cycads. I guess you can give it a try, but definitely dont expect it to work (if the entire "log" was intact then it actually would have a decent chance of rooting and making fronds). If this was a tree fern, it would likely survive, but as a cycad, I dont think it would make it.
-Alex

sometimes you can root those. coat the bottom with rooting hormone and let dry a week. Cut off all leaves. Stick in pure pumice and leave... keep in heated greenhouse or some place warm and out of sun. Do not water. Check for root formation once every 2-4 weeks. May take a long time and never happen at all, but it can happen.

Sometimes,the mother log rots-but pups form. I'm sure you would prefer the 6' log to root,but in Hawaii thats only 5-6 years time for those cycads.

Thanks for the replies and the welcome!

Would cinder be an acceptable substitute for pumice? And by no watering, does that mean leaving the cinder dry, or should it be moist?

Aloha,
Kala

I think cinder would be acceptable. Dry is better, though in Hawaii, all will be moist eventually.... just don't add any extra water