Current firmware does not support selection of the matrix send point. This is being considered for a future release.
Yes, using the matrix out for the PA is a good solution. My typical mix setup is to work with an LRSub main mix (separate feed to the sub bass speakers), then route the main LR via stereo matrix 1 to L and R of the PA, and the main Sub mix via stereo matrix 2 to Sub of the PA. Of course I only need one feed from the Sub stereo matrix but the advantage that gives me is the ability to gang GEQ on those two matrix so that I have instant access to one graphic EQ that affects the whole PA. Stereo matrix 3 and 4 pick up the main mix for a couple recording feeds which are not affected by the main PA EQ. On the surface you can bury the main L, R and Sub masters on a layer you don’t use and then control your main mix from just two strips assigned from stereo matrix 1 and 2.
But that is just one way of working to achieve what you want…
Regards,
Carey (A&H)