2003 Fondriest U107(him) 2003 Marin San Marino (her) Meridian 26" wheel "enduro" tandem; coupled 2007 Zona plastic tandem
It might be worth writing to Winwood to see whether they would endorse the use of their Dusty cross cyclocross fork for use on a tandem. As I recall, their disc brake model has been used on some tandems. The Dusty is available with carbon blades, and 1" aluminum steering tube.
Wound Up can make you a 1" tandem carbon fork for somewhere in the neighborhood of $500. You have to go through a dealer or bike shop to order & pay for it, but they'll answer your questions via email.