I use the smallest size panniers Arkel makes (18L?) and a frame bag and a pair of fork mounted straps by Cleveland Mountaineering.
My first tour I only had the panniers and was packing 15 lbs. I decided I really needed to take a couple more things on my second tour so I just loaded them up on the rack but since my touring bike is just a regular road bike w eyelets, having the extra weight mounted high made the bikes handling kind of iffy.
I got the frame bag and the fork system just to spread out the weight. A ride in the desert means the fork bags are loaded w water. Going across BC/Yukon I had all my rain riding gear in one and my tent in the other.
I don't have a big frame (i'm 5'6") & the frame bag goes around a water bottle so it does not hold a lot but I put small stuff in there thats relatively heavy. The toiletries bag goes in, bike tools, maps.
All this leaves my panniers lighter and with some room left if I need to load up on food for a long stretch between towns.
This set-up has worked very well for me. The spread out load has made the bike handling issues go away. I'm still pretty minimal @ at less than 20lbs but I have enough capacity to carry what I need. Walks in Trees was concerned about feeling a sail like effect, I have yet to hit a really bad cross wind on the 3 trips I've taken since I got this stuff but I have not noticed that being an issue to date.
I'll give a shout out to Jeremy Cleveland @ Cleveland Mountaineering. His "Everything Bags" for the forks is an excellent set-up and his frame bag fit perfectly, was reasonably priced, and done in short order. he is also a great guy to deal with.http://cleavelandmountaineering.blogspot.com
And if you want to see my set-up, my bike is the bottom picture on this page, the light blue Spectrum.http://cleavelandmountaineering.blogspot.com/p/custom-frame-bags.html