JAZZCNC, in general I understood all issues you wrote about these machines and I appreciate that honest temper used to describe it all.
Why people buy these mainly because can't find any better on this price level.
But now thanks for given information I can see more clearly what to expect from Heiz.
Right now I'm not in a position to spend time building my own machine, so I will definitely buy a ready to go set.
So the next step is to keep searching for machine with proper frame, supported linear rails and ball screws.
Actually yesterday evening we started to look on Al series from team-haase.de
These machines seems much better compared to Heiz.