I've used the inflatable version in that size and yes you are correct it tends to move around less than the smaller pads. It was in one of those folding seat sleeves so that may have helped keep it in place by being less slippery.
The part I liked best about using the pad is that it completely eliminated any calf ridge I had with my Blackbird. I probably prefer a bit more air in it than was recommended in my reading here on the forum. Your results may vary.
I really like this setup for indoors or in the back yard.