Its all on how you make it. There is no play in mine at all. I made mine so you have to slip it up under the top arms, and then rest the it on the bottom arms. then the reverse to get it out... Its very secure and never had to worry about it falling. I drive in Cleveland, so thats saying something.
. I took a fine file and filed and sharp edges made by the pliers. Then after a couple of coats with spray paint, its like I bought it from somewhere. I use no buffers and have marks on my case from my holder.
I've made a few (about 10 or so for a different phones) the key is just to take your time and make every bend as perfect as you can.