This thread is borne from a well known (to me) problem. It started with a custom stem that is well outside of 'normal' stem dimensions (thread elsewhere on this forum) and has progressed to doing unnatural things with the seatpost.

As many of us know, our bodies adapt to life, we become less flexible and weaker; we get injured, we age. At some point, we don't need adjustment, we need dramatic change. I think the OP is at that point. A gallant effort has been made to adapt the existing tandem frame to the riders needs but, a line has been crossed and it's not an adjustment that is needed, it's a new configuration.

PromptCritical It is time to pay our debts that we have incurred to this point and find (or order) a frame that fits our current needs.