How do you use multiple monitors in MS Remote Desktop Connection Manager 2.7?

Using the RDMan from:

https://www.microsoft.com/en-us/download/confirmation.aspx?id=44989

Tools->Options->Full Screen-> last checkbox is 'Use multiple monitors when necessary'

however this has no effect.

**This question is specifically in reference to RDMan, a Microsoft exe that manages multiple RDP sessions from one window (NOT windows's builtin rdp, i.e. mstsc from the runline, they are different softwares).

Works fine using mstsc:

RDMan is on Win7

Host is on WinServer 2008 R2