I had tried ping pong balls before (under the nails) and could not get them securely attached. I was successful yesterday and it was easy. I did two things that were different than before.
1) My nails have a 'shallow curve' across most of the nail (less than the curve of a ping pong ball). But they REALLY curve at the far outside edges. So I simply cut the ping pong balls to stop barely inside the point where this extra curve starts.
2) I used my Alaska Pik's to hold the ping pong ball material firmly against the nail while the Crazy Glue set (say two minutes). So the setup was to insert the ping pong ball material (glue on the nail side) between the Alaska Pik and inside of the nail.
This actually worked easily and seems to have worked well (for 24 hours anyway).
So I know have a real nail on 'i' and 'c', Alaska Pik on 'p' (not enough nail to install a ping pong ball), and ping pong balls 'a' and 'm'. Alaska Pik's were OK but they somehow felt 'clunky' and I had a tough time getting them to feel right on rest strokes. But they were certainly better than the no nail alternative (I am not saying that no nails cannot work, just that this requires adjustments that I have not made).