Thanks for all the details. This indeed looks easy. I started checking details of the mounts and indeed Topeak is beveled and somewhat complicated. I did not get to the original Shapeways one and it may need to wait for the weekend. In a certain sense, on our side we decoupled ourselves from the mounting dismounting issues for any particular mount as we switched to velcro for attaching and detaching - the original mounts serve only for placing of a velcro covered pad on handlebars or elsewhere. In that way we do not rely on any particular uniform system across bikes, phones and other devices, pouches etc. The system stretches to cars, wrists etc. Topeak I think also had some car mounts but we went ahead our own way. The commercial ones were too rigid, too limited and now we just use pieces from this or that.
I went from a Delta case to the Topeak and am always looking for the "perfect" way to mount my phone, I run a Dynamo so my phone doubles as my bike computer and I like to have easy access to it. How does the velcro work, do you glue 1/2 to the case and the other half to something on the bike? I think I'd be too paranoid to attempt to mount my phone only using velcro.