Found some help at this Jive Site:
MX700 and MX800 - Wall secured Floor stand
The current CADs and install guides for the MX700 and MX800 versions does not specify the height of the screw holes for the bracket securing the system to the wall when using mounting "Option B" (Floor stand, Wall secured). The collateral will be updated, but in the mean time will the attached image provide the necessary information to any customer that wants to reinforce their wall for the wall secured floor stand. The measurement is identical for both the MX700 and MX800.
https://cisco.jiveon.com/groups/collaboration-endpoints/blog/2015/08/04/mx700-and-mx800-wall-secured-floor-stand