Idea for PTT switch
If you are going with rear controls, try on top of the stick, if the controls are not full time, just place a swith in a easy to reach spot that wont get kicked or hit when getting in or out, if its for IC, just go with VOX and unplug the set when not in use.
I am putting my PTT switch on the throttle quadrant where we military types are taught where it should be and activated by my thumb and a VOX IC.
I am pretty sure that Aircraft Spruce has one that connects between the headset and the connector in some way, when I was in the back of the AC I was the FE on, we used somthing like that.
There are some ideas...