A few people seem to have failed on the radius of this.

How come? What's the radius stipulation?

Used the standard Sierra knob as I'm sure others have ,with no problems

I think it's <2mm is a fail, but not sure now...

Steve

actually it might be <1.5mm

I'm one of the fail people!
I used an aluminium knob with the flat top for a badge from Europa. Failed on the radius at the transition between the 'ball' and the flat top. Replaced it with a spherical knob for the retest - now has the dodgy one back on!
This was the first thing the tested noticed (the tested was being tested at the time too which didn't help!).
Once I knew it had failed, the rest of the test was much less stressful!

yep - same here - the top has a cut in for the central emblem with flashing LEDs*. - the sharp edge fais the radius.

I made my own from a bit of wood and spray painted it - look quite good (but fitted original one back on)

* I didn;lt buy it and the battery no longer works so no flahsing.