Originally Posted by
Eulers
...Will a 140mm hub and 40-spokes (20/20) properly support use of 11-speed with a 295# husband/wife team?
Without any problems. You could easily use a 32H wheelset with some modern rims. For the money and effort, you might be better served going 3x10 and using Tiagra 4600/4700 series levers. That would allow you to keep your wheelset and crankset. You could also upgrade the OEM crankset by adding modern chainrings with shift ramps. You're going to pay a fortune to make an old tandem 2x11....
Do you have a rear drum brake? If not there are some low cost rear hub options for 32H/36H.