I still would love to figure out how to make the L and R just two different monitor mixes but I guess I'll just have to stumble on to it
you won't stumble across how to use the main left/right for two separate monitor mixes because it can't be done properly.
HOWEVER... the L/R can be used for two different monitor mixes, BUT.... BUT.... many things will not be separate,
equalizers, compressors, gates, will all be the same for both L & R output channels.
For instance, there is only one master fader for the Main left right which means both mixes will have to share the master.
The only way to get two separate mixes is to use the pan slider to set which channels go left, and which channels go right.
If you try this... make absolute sure that all your monitor mixes are set to PRE fader.
The correct answer for your problem is to sell your mixer on eBay, get what you can for it and then buy a mixer with more mix outputs like the DL32S.