Ummm, Indy, I can barely do a regular plank, never mind pick up one arm! Hence, my troubles on the bike!
Miranda, I think the fit is correct. The 56 was too small.
The LBS was really good about rechecking the fit. They advised that they can do things like change the stem, raise the bars, etc, but that I should spend some more time riding and getting accustomed to the bike and new position. If, after some time on the bike, I am still uncomfortable, then we can start tweaking. Today was already better than the first ride.
Also, I started doing Weight Watchers again, so hopefully taking some weight off will help. No more donuts!!!