May have to modify the mount for a RAM ball.
I have that mount permanently attached to a RAM removable mount, the one that slips over the the little round disc and locks on.
I slide the thing onto the ram mount until it clicks, plug power cord into phone and put into case. If you look, there is a little plastic loop piece under the case. It comes with an "Oh $hit" strap. Strap attaches to bottom of case ands there is a quick release to attach to the other strap which is attached to steering stem. That way, in the unlikelyhood that the mount should fall off, it will be saved by the strap.
I remove the whole thing whenever I park it (takes about ten secs) as I don't want someone to come by, break it off the bike then later discover that there is no iphone in it.