I dont trust the IAT to compensate enough for the additional nitrous. I think the Mapswitching with the stock ECU is the best way to do dry shots. We're running two bikes with bars, two fogging the box and I'd say the difference is negligable from a riding perspective. I would say a 30 shot should be tuned no matter what, whether your running dual PC's or Ms through the ECU. if you want it to be simple, go with a single fogger, map switching and have a blast.
to the OP, if you would like to know how we've got three bikes spraying with the stock ECU pm me and I'll give you a quick walk through of our simple setups. IIRC you can run on the stock ecu then switch to a PC for a nitrous map, but I've never set a bike up like that, so I wouldnt be able to say much about it.