I don't have the photos to post to prove it, but my solo bike and the captain's cockpit are identical down to the mm. I know what is comfortable and that is what I want. That is my story and I am sticking to it!
Bars on my single are 3" lower than tandem.
Seat on single a fraction of an inch lower than our tandem.
I do ride a bit more aggressively on single than on tandem.
Both bikes are custom and fit me perfectly.