I too have had a hard time finding shorts that work on the tandem. I have a Terry Butterfly saddle on it - and I'm probably going to change it out for a Brooks.

I wore Castelli shorts on the Death Valley Century last weekend (it's actually 105.2! miles) and really liked those. The Pearl Izumis have a lot of padding on the inside of the legs that just really bugs me.

A note about suspension seat posts - on a rough road, the nuts holding them on can be worked loose. Fortunately, I didn't find that out until after the ride was over!