better mix out, fader control

we have the SQ5, we need to separate our sub and main outs, so that we can pull certain channels out of the subs. but i don't want to have to go to two different pages in order to change the output level of one channel in both the subs and the mains. I need my LR fader for every channel to fully control all of the levels sent to the mix out. selecting 'post fader' for each channel does not accomplish this. it offers partial mix control, but not full. I need each LR fader and mix out fader to match identically. perhaps I'm doing something wrong when setting a mix out channel to 'post fader' but i don't see how.