Sometimes there is no substitute for personal instruction.
Lots of possible issues that are difficult to guess over the internet.
There are a couple comments mentioned above that cause me to think of possible strength and flexibility issues that we cannot see. For example, the need to lock elbows when standing mentioned in the original post. From a safety perspective I don't believe that locking elbows when riding a bike is ever a good idea.
Bikes are great machines but it does take a minimum amount of strength and flexibility to ride any bike safely and especially to captain a tandem.
Last edited by waynesulak; 03-19-16 at 09:50 AM.