Since Bullet Bob made sure I saw this thread, I'll throw in my $.02.
I'm using the RAM Universal Handlebar Mount (similar to
https://www.rammount.com/part/RAM-B-149Z-PD3U - I don't have the rubber booties for the upper and lower hooks). Even though it's spring loaded (the upper hooks slide up-and-down), I've used it with two different models of phones with good success.
My current phone is large enough that it
just barely fits, and I have no worries about it coming out accidentally. With my old (smaller) phone, it was
real easy to slip the phone in/out with one hand. That worried me a bit, so I engineered a pin (straightened paper clip) that would keep the sliding part from moving after I got the phone in. All that took was a well-positioned hole drilled through the fixed part and into the sliding part.
Your best bet? Make a trip to Iron Pony. They have a wide variety of RAM mounts in the store, and your can test fit your phone until you find something you're comfortable with.