YES this is possible.
You probably find the answer in the forum because I have replied several time.
You just have to defined the replication rule in the JMS templates and after use it.
See tutorial video 13
www.jms2win.com/tutorial#jms12x-13 that show how to use JMS template. You can also have a look in the video 16 that also use JMS templates to share the users.
www.jms2win.com/tutorial#jms12x-16
Create a JMS template
template id = replic_master
template site = select the "master DB"
Create a slave site
Site id = slave1
domain = copyMainSite.mydomain.com
Template site = replic_master <======= This is the rule that you have defined
new table prefix = slave1_
Deploy directory = the place that you have choosen in your hosting server for the copyMainSite.mydomain.com subdomain