ZBrushCentral

Can you Take just a head and turn it into a full scale model?

I have a head model i did that has a decent amount of detail to it. I was wondering is there a way to add onto the head? I’ve tried to sculpt out a body off of the head but it seems once you start making it larger it wants to spike off… and smoothing just seems to erase it for the most part. Any tips would be highly appreciated.