With regard to two copies on canvas that depends, you have either hit edit twice, or you are getting what happened to me as well. I have found that it doesnt like to be sculpted over the same area quite quickly and it 'bugs' out and dupes a new copy. It happened a couple of times in a new tute for SM that Im doing.

I may post this problem on the Zbrush Central forum

Thanks CGI, yours is looking good so far....

Jay