Well I've managed to get these fitted up with a bit of a struggle and teeth gritting.
It was a small alignment issue with the head spigots but no biggie.
I loosened the 2 holding bars for the rack which was enough for a bit of give and a bit of persistance and they gave in eventually.
I'll also slot the screw holes in the holding bars a bit more as they are a little bit tight to reinstall all of the screws.
Mike, I haven't checked the frame for clearance but I'm sure that we can work around that one way or another.
Here are some more photos with the Mikunis mounted up to the Stage 4 Head.