last summer I met two women riding across Canada and were loaded with about 40lbs or so. The one with the 920 had all her load on the backat first and had numerous spoke breakages--not much of a surprise.
as you mentioned, not having a triple is a stroke against, alum frames are fine in my experience (and friends who have been riding alu frames for decades) but the wheelset really isnt ideal for loaded touring. The one example I have to support my wheel comment may have been an anomaly, but I doubt it, again, from my experience this is not a surprise at all.