I use a RAM yolk mount with an iPad Mini. I mainly use this iPad for IFR plates but occasionally will have it on map view for en route SA with WX.
I also use a full sized IPad Air on a knee board. This one is used for flight planning, as a scratchpad for copying detailed ATC instructions, en route SA, WX, etc.
Both of them have ForeFlight coupled to a Stratus. You certainly don't need 2 iPads but I like the redundancy and the Mini is great on the yolk with IFR plate loaded up. Also with ForeFlight Pro the moving airplane helps you keep up with your position on the plate as you are starting your approach. This is NOT to be used as primary navigation for an approach (I use my plane's GPS/ILS/VORs for that) but the added SA is nice to have. On my IFR Checkride the examiner commented that she really liked my setup with the dual iPads.