Cyclemorph is a complex and rather expensive idea and really you still don't have a tandem.
Get to test ride the Sierra and the Zydeco and see which you prefer. Especially check out the ride/fit/quality between the two brands and the comparative braking power.
The $600 Schwinn (that literally fell apart) we had reference to was NOT a Sierra but a really cheaply constructed and over-priced geared cruiser type. On its maiden voyage in Duluth, MN last year, we stopped our tandem to assist the Schwinn stuck by the roadside with a stoker's rubber platform pedal that just fell apart; it was cilpped
together and really not fixable. Stoker had to continue riding with foot on just the pedal axle . . . and they had just paid cash for that 2-seater that very day. Suggested they go back to the bike shop and have them put on some better pedals, for both pilot and stoker.