yea no 40 spoke XT's.. that's why I suggested buying their tandem hub, they come with a 140 or 145mm wide axle,
but the axle's thread is the same 10x1mm , you just need to be a bit clever, and change the left end spacers and the length of the axle.

I read Aarons bike repair in Seattle uses tandem Shimano hubs, and does that,
to build beefy rear wheels for their Big Dummy , Xtracycle builds for cargo hauling purposes.