After much playing and tuning (and help from my brother in law) found some good stuff about using SRS in the cat. First, this is ONLY built into the Cat (TY Heatblur for still being the most awesome dev ever!). There are controls for your ARC-159 and ARC-182 radios. These are typical like with the Hornet, tune to the station, hit that button and brings up the radio menu in the top right. Default for those are RAlt + \ and RCtrl + \ respectively. With the Cat however, they also have one for SRS only without the menu. This allows you to talk over SRS without the menu to pop up and annoy the crap out of you. See here:

Next, found how to use the intercom between pilot and human RIO for SRS and how to get it to work. In your DCS settings, find in the Radio submenu 'Mic Button ICS - SRS Only / No Menu'.[size=78%]

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Assign a button to this. Now open up SRS and find the 'Intercom Select' button and assign the same button to it. In my case I use a modifier key so you also need to set that in SRS under the 'Intercom Select Modifier'. Don't worry about it if you don't use one.

The last step is once you and your RIO/Pilot are in the bird, turn off the Hot Mic.