[bojan]

Hi Ken, this is also an option, thanks for suggestion..
Do you know how the PVC behaved on high temperatures (sun)? I will have 130kg of dome on it (hmmm, the weight will be distributed along the length of the pipe through the wheels.... and the pipe is supported by the recession into concrete.. food for thought.. maybe pipe should be filled with concrete? cheap and easer than metal but possibly good enough.. I will try to experiment when the time comes.)

EDIT:
Being PVC, I imagine it is easy(er) to slightly adjust the final radius of the curved pipe base runner, by simply tightening some kind of the rope (steel?) inside, before filling it with concrete)... so for every cm in radius, the circumference (the length of the rope) must be changed by 6.14 cm..
Interesting...