I use an iPad Air but am going to try my fiends iPad mini. Air is a great size to have, but I will agree it is a bit big but nothing that truly makes me want to not use the larger. However, I will say that the iPad mini can fit in the case, which is a pretty great thing.
How tight is the grip of the holder. If you use a neck strap, are you concerned the iPad Air will follow out if you just let the controller dangle from your neck?
After trying both configurations I settled with the iPad Mini. The size is perfect for me personally and I love that it fits in the travel kit perfectly
I started with an iPad air2 128/cel and switched to an iPad mini4 128/cel, I am much happier with the mini setup for the phantom and save the iPad Air for the couch...YMMV, Different stroke for different folks stands true.
<edit> I'm waiting to see someone make an adapter an utilize an iPad Pro!