Mainstage, Ableton and APC20

Hey all, quick question - I'll try to be brief and to the point.

I am using Ableton Live for running tracks along with Mainstage for playing software instruments live. I will be using the APC20 to control Ableton for the most part, but there are a few controls on the APC20 I'd like to use to control Mainstage like for switching patches and changing volume and a handful of other things. However, Mainstage is accepting signals from every button/knob/slider from the APC20, therefore, effectively hindering my live play. With Ableton, no midi controls are assigned until I assign them. Is there a way I can stop Mainstage from accepting every midi signal except for the few I want to setup?

Any help is appreciated. I've been working on this for 2 days and can't seem to manipulate it how I want. Thanks!!