Hi John,
I have fitted ballscrews to my X1 and as you say it is a bit of a squeeze especially for the X axis nut.
Not sure about fitting the Arc-Euro ballscrews as thay have a flange which is about 26mm high and will not go in.
The other problem I had was that of machining the Y axis to take the ballnut fixing for the X axis as I only have the X1 mill, to that end I obtained a spare Y axis casting from the States.
I dont have any drawings or pictures, all done on the fly I’m afraid.
Biggest problem I had was in machining the ball screw ends and threading them ,baptism of fire was no exaggeration.
Peter