Mixbus routing


I am putting 2 S16s in 2 racks with 2 Furman Voltage regulators onstage. This makes shorter xlr cable-speaker/power runs and all power under my regs. The mixbus part is tough, though. 


I'm using 1-6 mixbus for traditional group mixing, 7 starts my monitor mixes, but 8 has to be for stage right speakers. I need 8 to also be mixbus 2... So is this is not workable because of mixbus organized in groups of 2? 

S16 #2 outs are 9-12 are mon mix #3-6, and  out 16 is Stage left speakers. On the board 13-16 are my fx. I'm a little confused as to how to set this up to use my S16's apart from each other. Thanks!