[--JawZ--]

No I have tested the IGUS system and it is not suitable for CNC machine use, even at Hobby level, it would be a very bad choice if you where to build a new machine, IGUS can be used for other sliding systems that don't need any kind of accuracy

The design you have with the round rails would not work with supported round rails as drawn the Bearings would have to be open, round rail bearings also have large clearance between the rail and bearing some have small adjustments that can be made but are ok for hobby level machines, if you want any kind of accuracy then you would use pre-loaded profile linear rails

I was talking more in general terms of cnc machines, a metal or even a wood router/mill cnc machine should not use IGUS rails, but a low weight 3D printer or a laser, could and can use the IGUS rails with good results.
I have however, not been able to do any long term tests of this kind of system yet. As I've recently just started testing the IGUS rails out on a custom designed 3d printer made up out of alu, carbon fiber and both IGUS rails and roller wheels in v-slotted extrusions. The design also welcomes the HWIN rails, so if my testing shows that I can't use the IGUS system, I will just move to the HIWIN system.

The design was just a mockup of a placement idea I had, and was constructed while I had some time of at work. No real design thought beyond the general placement was considered.
And I agree with you, that pre-loaded profile linear rail system is a better option. It was just to add an option of something someone might think of, and having it in here with both pro's and con's. Which would allow them to decide to choose a similar, or different design. If it would fit most of their requirements, not only in the machine, but also in their pocket.