I'm no expert, but it seems to me that the forum is setup exactly the same (style, mods, language, etc) and the actual sections are different (F=2,3,4 on one and F=5,6,7 on the other) that it should work fine!
In my mind it's similar to moving your board to a new host. You move your database to the new server, upload the files to the new server and set the config on the old server to point to the new database. You then initiate your DNS changes.
My point is at times during the DNS propagation you actually have two boards using the same database!