It's really a moot point. If you're 10" apart in height and are both strong cyclists, you'll find it nearly impossible to find a "stock" upright tandem that would fit your wife in the captain's position while giving you a proper fit and enough reach in back as the stoker.
Even if you expanded your shopping list to include a custom-sized frame, it would be a tough fit and I'm still not sure your wife would be able to handle the workload as captain given your height.
Back to the basic question...
All things being equal, the key attributes of a captain are:
1. good bicycle handling skills
2. good communication skills
3. the ability to subordinate their skills for their stoker when necessary
4. adequate upper body strength for any given stoker who will ride with them on the tandem
5. large enough body mass to allow the stoker to ride in their draft
While some tandem teams could get around the "captain holds up the tandem" scenario by adopting a synchronized start and stop technique (as opposed to what Bill McCready has coined as "the proper method"), the one thing that can't be worked around is the upper body strength requirement. More specifically, the taller the stoker is and/or the higher they carry body mass the greater their influence on how hard/fatiguing it will be for the captain to control the tandem.
The three most demanding circumstances are:
1. Countersteering to arrest the momentum created when a tandem is leaned over into a hard turn and to stand the tandem back-up to complete the cornering manuever. The higher up a stoker carries their weight, the more pronounced the momentum will be, thus the greater the effort required on the part of the captain. This is why most captains find themselves to be much more fatigued on fast, twisting mountain tandem descents than when doing the same descents alone on their personal bikes.
2. Countering unintentional but very normal side-to-side movements or weight shifts by the stoker with countersteering inputs. More specifically, when a stoker leans over to grab a water bottle, turns around above the waist or extends an arm outward from the bike the CG shift to one side and causes the tandem to lean over a bit. When a bicycle or tandem leans to one side or the other, the front wheel will want to turn the opposite way and initiate a turn in the direction the bike or tandem was leaned towards, aka, the wiggles that you feel on a tandem. To keep the tandem going in a straight line the captain must counter the front wheel movement with handlebar inputs and you'd be amazed at much of this you do, almost without thinking, as a tandem captain. Again, the taller or higher the mass is on the stoker the more pronounced these movements become and the more effort it takes to counter them.
3. Standing & climbing or sprinting out of the saddle. All bets are off on this since some teams are smoother than others. However, in a worse-case-scenario where the team is not smooth or likes to throw a bike back and forth as they climb or sprint holding it to a straight line can be a bear.
Most tandem captains who have never had to pilot a tall or top-heavy stoker will not have an appreciation for how challenging or fatiguing these things can be. Me, I thank my lucky stars that my Debbie is a little china-doll. I've ridden with taller "quest stokers" on board our off-road tandem and it always comes as a rude awakening when I realize how much I take for granted on the size differential. My hat is off to the captains who routinely pilot tandems with tall and/or tall and large stokers. Again, it's the height of the mass that gets you.
Last edited by livngood; 02-01-04 at 11:27 AM.