As I said, I have purchased a nice milling head that goes together with my lathe.
This lathe is Chinese made, sold by a company from Austria which is quite OK.
When I installed the milling head, I found the attachment between the column of the mill and the bed of the lathe as a weak point.
It is made of only 4 screws, not locking very well the column in rotation.
I was looking at the best way to improve that in order to avoid any rigidity issue. I was about to install some screws in the joint between the column and the bed, to avoid any relative movement when suddenly, the light came !
Eventually, I finished with this solution :
It could not be stronger nor stiffer !
Of course, I made oval holes, and used a digital angle gauge to set the column perfectly perpendicular to the bed before tightening the screws on the wall.