I've bought tandems for friends. Bought my Dad and his list of ex's a Cannondale, bought my friend a Burley. Neither ever get ridden so far as I know.
Best 27" rim that is tandem rated that I know of is the Velocity Dyad in 48h. Paired with a used Phil Wood hub (one piece alloy shell, not older two piece) and built by either Peter White or Wheelbuilder. That's my recommendation. I'd avoid any Amazon or eBay built wheel like the plague.