I have a road-style touring bike (Kona Sutra, great name!) and a 29er mountain bike and on both, I have been using the saddles that they came with which are very similar in shape, both made by WTB. For the most part, I've been happy with the saddles as they are but lately, I've been doing longer rides with the 29er, taking it out to camp (depending on my starting point, it is a 66 or 72km ride) and I've been suffering with saddle sores (zits) showing up a couple of days after the rides and some chafing. I'm wondering if I need a different saddle for the 29er than the one that I'm currently using which is probably fine for shorter rides but may be the source of the problem for the longer rides. The touring bike is ridden on the drops so a more lean-forward position whereas the 29er is ridden in a more upright position.

Does anyone else have 2 (or more) different bikes with 2 (or more) different shapes of saddles that are purposely suited for the body position used on the different bikes?