Hi florian,
beg your pardon for the delay.
Unfortunately was Sara extremely busy at the fair and we couldn’t verify for 100% if it is possible to change the bottom tubes without problems or not.
Principially it seems possible, but to be sure we have to check ourselves.
I’m highly interested in this modification and do have several suggestions how to start, but I think it would be better to talk about that first outside of the forum and present the results to members later.
If you are also still interested, would you mind to mail me in private?
(Mailaddress already in your post box - upper left corner after login.)