Update: Finally got this to work. Just enter the HTTP server location of the software, generic configuration, and now even the contacts csv file (new feature in 2.1.5.2) as DHCP option 67 if using the 3300 as the DHCP server. No idea why it wasn't working when I first started messing around, but it works like a champ.
I'm just using IIS on my Enterprise Manager server to host the HTTP site, made a folder for the UC360's and then a subfolder for each site so I can have a site-specific set of files that contains everything but the SIP login/passcode for each UC360. Set the DHCP option for each site to that site's folder on the server. Then all we need to do to install a new UC360 is plug it in and go into settings and enable VLAN, and the rest comes up automagically.