Scott,
unfortunately there is nothing we can do about it. Since the feature you are asking for has to be implemented on the server side.
By the way, if you are using UltraVNC, be prepared for a surprise. UltraVNC supports three monitors only. The magic number 3 is nicely hard coded in there source code. We had implemented more than 3 monitors support for one of clients and probably will submit these changes to UltraVNC. But if I remember correctly there are other problems with multi-monitor implementation in UltraVNC.
PS: migration of Repeater settings has been fixed in 3.5.17.1. It's going to be released with in a day or two 