Hi Ellen, Glad you are enjoying (mostly) your tandem. I have half a dozen saddles in a box that I tried before finding one that worked for me. Some times it is a matter of trying lots of different ones. I will say I'm a fan of modifying equipment until it works better and the saddle I use has been heavily modified. However, some saddles for some people are very sensitive to tiny changes in not only saddle position, but rider position. You might try moving the saddle up or down a few mm at a time or front to back just a bit.

If there is some issue with a leg length discrepancy or hip imbalance, the idea of trying a paper towel shim, as suggested by Velodog, is easy to try. If the shim seems to work, a permanent one can be inserted using ski boot shims. http://www.tognar.com/bontex-insole-shims/ If home remedies fail altogether, then begin a search for the best bike fitter in your area.