I envy you guys that have been able to keep your triple chainrings and make them work for a double. I started down the rabbit hole of "I better find a tandem 11-speed double first" and now am committed to that.

I'm looking forward to Di2 but I'm not sure what spares I'd would want to bring along. For me it's been long shift/brake cables and a derailleur hanger. Having just completed external routing of Di2 on an aluminum tandem frame, those tiny little wires seem like they'd be a bit fragile. So maybe an extra wire or 2.