I have been looking for a cleaner iPhone mount to fit your mount. I contacted the makers of Podium by Pivotal; but their socket is 12.5mm, where yours is 17mm.
However, the CEO said they are working on auto adaptive mounts, and are interested in your design. You may want to contact them, or check out their product.
Podium by Pivotal :: Rotating iPhone Stand iPhone Dock iPod touch Stand iPod touch Dock
p.s. I have no stock, etc. in this company. Just trying to help you, myself, & anyone else who wanted an iPhone attachment!