Agree most effective way to loose weight off the tandem is for the duo to push away from the table; if you undulge: lay off the beers/booze, sugar coated stuff and yes, even skip dessert (most of the time)!
This captain loves desserts/sweets, however standing order is dessert (maybe!) every other day.
This coming from a guy that, in his younger years, after a century, could go to an all you can eat place, and held the record for only having 7 desserts! One time eating 3 full banana splits (with all the goop and nuts and cherries and stuff) after dinner . . . with the owner of the restaurant offering the 4th split free . . . asked him to give me a raincheck on that. My riding weight then was a 118 lbs.
Thirty-some years later he's 'balooned out' to 135 lbs; stoker's weight is 108 compared to her 98 lbs 53 years ago. Now we order 'senior portions' and have trouble cleaning our plate!
Lighten up the bike: C/f fork and very light (rotating weight!) wheels will make a difference.
Fork suggestion: either Reynolds or Alpha Q tandem fork.
Wheels: Topolino tandem wheelset (c/f spokes with kevlar coating) or Rolf Vigor Tandem set.
For a bit more comfort: c/f handlebars and stoker stem/seatposts.
We utilize Dura Ace calipher on front and Tektro Mini-V on rear for brake.
BTW a real good looking tandem duo (but do suggest captain tighten helmet strap a bit)!
Pedal on TWOgether!
Rudy and Kay/zonatandem