My double-blade is a 9 foot long metal-shafted thing.  I've gotten a fair amount of use out of it but I doubt I'll be carting it with me much going forward.  Maybe if I would just spring for a lightweight alternative I'd change my mind.  The last couple times I didn't use it all that much and it amounted to simply "one more heavier item that had to be portaged."  On the other hand, there have been times when I've made a reasonable commitment to using it and getting my stroke just right, resulting in the satisfaction that I seemed to be "flying down the lake."  It takes a little commitment and practice to getting it right.  The older I get, however, the more tiring those shoulder motions seem to be... and the best use of my metal double-blade is to prop up my kitchen tarp back in camp.

Bottom line: that particular paddle is staying home next time and, unless I find a great deal on an ultra-light 9 footer, my "back-up paddle" will be another lightweight bentshaft.

The double-blade takes some commitment and practice to become comfortable with it.  It CAN be a nice alternative to paddling all day long with a bentshaft.  However, it you haven't developed that comfort zone with it BEFORE you head into the woods, my recommendation would be to leave it home until you do.  People tend to stay in their comfort zones and the double-blade can become dead weight... of which I am already far too much of a collector on my deep woods trips (which reminds me... anybody in the market for a pink wind sail?).

As far as the rocking-from-side-to-side goes, I believe ST's comments are right on the mark.

Jimbo   8-)