...I already said I would be using p-clamps or something similar. I have a seatpost mounted rack right now, but as was mentioned, it can sway quite a bit with some pounds in the panniers. This is why I was looking at other options.

The Tubus fly looks really good, I might have to save up for that one. The axiom rack linked above looks like a great concept, but I read a few online reviews that point to some design flaws. Namely that all the important mounting points are thinish flat stock.

Any other recommendations?