switching places
 

we are looking for a used tandem that the wife and i can switch as far as captain and stoker but can not find the right size , we have tried ebay and craigs list-- there are no tandem shops within our area, can anyone help

tandemmag.com classifieds. Craigslist in a larger area. Local bike shops also often keep listings of local tandems for sale even if they can't keep them in the shop.

Are you about the same height?
Look for a Co-Motion Periscope (ultra adjustable: seatpost-within-a-seatpost) or a Bike Friday tandem

i am 5-10 she is 5-6

With a 4 inch height difference, there may be a fit issue for switching.
But as mentioned before, Co-Mo Periscope or Bike Friday are very adjustable.

Actually, women typically have longer legs and shorter torsos for a given height than men. So four inch difference in height might mean quite similar leg lengths. Or not. Averages are only averages, and the variability is significant.

If the two riders fit the same size road bikes, it shouldn't be too hard to adjust saddle height and stoker stem length. Captain saddle-bars distance will be optimized for only one rider, or a compromise, though.