That is a very small cockpit. I think I'd do the lap thing in there with some way to keep it from flying up and whacking me in the face. In the right seat I like to have it tucked into my spiral steno pad I use to copy things and make student training notes about the flight. That whole thing can be quickly stuffed into a side pocket or put on the floor or in smooth weather will stay put on my lap if I have to grab for the yoke while saying smoothly and professionally "my aircraft" as I'm about to be killed by the student. LOL.
(My CFI has repeated this phrase so many times I can hear it in my sleep... "Never have anything in your hands below 500 AGL, but don't let the student know you're ready to grab the controls. It'll destroy their confidence. Keep those feet lightly on the rudder pedals too.")
I haven't had one hit me in the noggin yet but I've hit the noggin itself on the headliner before in turbulence and I've had the iPad go flying into the back seat or at least down beside it.
At least in the 140 it's not going to slide too far away on the floor!
Worst case scenario is it slides forward and jams the rudder pedals. If that happens the iPad is going to die before l do. Crunch.
I had a fascinating problem once in the Seminole. Thankfully just prior to landing. I put the iPad that was on my lap into the back seat without looking.
What I really did was slide it between the back seat and the carpet into a tiny little one inch tall space between the seat and the floor that has a lip in the front. After we taxied in the iPad was "missing".
Took me a few minutes to realize where it went and a few more to poke fingers and other stuff in there to get it to slide to the side of the aircraft from the middle where it could be retrieved. The paint stirrer that was the fuel dipstick came in quite handy.
I swore for a couple of minutes there I was going to have to ask the CFI how the back seats came out so we could get to it. LOL.