I finally got to try out my new rack today on the Jamis on a ride to the Natural Grocer for a few things. (DH is nursing an ITB injury, so it was just me today.) It worked great! In my Arkel Tailrider I had two cartons of coconut milk, a jar of tahini, bottle of tamari, and a large can of garbanzos. Heavy stuff. This left me with much less of a load in my backpack than I usually carry. The bike was heavy but rode well -- glad for the granny gears for a couple of climbs home!

Here is the rack we both got. REALLY like it as it's super sturdy and has many attachment points, unlike some of the others we looked at:

Blackburn SPX-1 Ultimate Seatpost Rack