The 'last post' was cut a bit short because I had to rush out & collect the wife from work.
Although the Solo and Tandem are geared the same, I find it easier to hold a higher gear (lower cadence) on the solo. Probably because the machine has less mass to accelerate.
I don't know how other tandem teams work, but in our case I expect the wife only to go with me and not complain when we're doing over 40mph downhill, followed by sharp braking and swinging round a corner at 25mph. And she's very good, she doesn't.
Chrissi obviously has to turn the cranks at the same speed as me but it is entirely up to her how much force she puts in. So she adds whatever power she can/wants to, and I do what I can. If that results in an increase of speed, I change up at a cadence of about 100rpm. If we cannot maintain speed and the cadence drops below about 80, I haven't the body weight to maintain momentum and so change down. I no longer need to advise my stoker of this action, we're both clipped in and she responds instantly a slight hesitation in the pedalling action as I change gear. It almost certainly helps that the Rohloff hub changes so quickly.
The only time I will advise Chrissi of a gear change is if we're grinding to a halt on a steep incline and I need to drop about 3 gears, because an enthusiastic stoker putting real pressure on can prevent the gear change from happening (even so it's still miles better than a derailleur).
Personally I think 44 x 16 is about as low as I'd want to go, because top gear and 100 rpm cadence means a road speed of about 30mph. And seriously, every time we go out on the tandem, we exceed 35mph, which is about spin-out speed for us.
We both prefer the tandem because the extra weight and the double power input smooths the pedalling action, we think.