The tilt seems fine on the few rides I've done with it but I don't tend to pull on the extensions. My riding tilt comes out about -0.4% which is about the same as my riding tilt on my road bike.
The stem mount is simply screwed through the bottom of the carbon tube. The top of the carbon tube is drilled away to allow the mount to sit in it. The small metal brackets are simply screwed into the carbon tube. You can see this in the bottom picture.
I have made another mount for my training bike and have attached it below. This is simply a piece of aluminium strip with the stem mount screwed to it and a couple of nylon clamps from bike reflectors (free from my LBS). This mount is easy to make and is solid.

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The RWS would still be handy for aero testing and also if riding in heavy rain but other than that it wouldn't be necessary with the ibike mounted as I have done.
It sits below my wrists and has a clean airflow and more importantly for me, I can see the screen easily without having to tilt my head down.
cheers
Steve