In regards to establishing this second store for the purpose of upgrading, it would be easier in the long run if you established a second database with the same prefix of your first, as that way you could transfer databases back and forth with ease. If you do decide to use the same database, you could have two stores off of one database with two different table prefixes. (Ie, one with no prefix '', and the other with anything other than nothing ie. 'zc2_')