Did it but it didn't hold on, the bottom is much thicker than the tube and the surface in contact with the shim i made from two seatposts was minimal. I appreciate all the help and sugestion! Thanx !)
@brigand: So, make a better fitting shim with more contact surface The right glue might also help. Ask our young friend, he once got the explanation how to bond stuff.
@Mr-Magura: The shim was not the problem, the frame design was, he did help me the first time. I'll ask him to help me with soldering, he is finishing the welding course.
It's quick, easy, cheap, and it works.
Magura