Outer diameter measurement of the aluminium tube is:
Minimum 24.8mm and maximum is 25.1mm.
And I am using standard 8mm fully threaded screws.
The tubing fits very tight every place else. Like the corner block, the lock on the roller and so on.
I think that it would be possible to enlarge the top bearing holes in the roller and then force the top bearings down. And in that way force the side bearings to press against the tube. Can you see any problems in the rest of the design if I do that ?