The message
from T i m contains these words:

But it all works (so far) but I wondered if I could replace the SS bar
with *tube* (of the same diameter) and would that better / (stiffer)?

No. Tube is stiffer per weight, but not stiffer per diameter. The only
way to make it stiffer is to use a stiffer metal or a larger diameter or
a different geometry.

--
Skipweasel
Pay no attention to that man behind the curtain.