I think my solution for now is going to be simply to unlatch the hook with my screwdriver at home, before leaving the house, if I'm going on a trip for which I plan on carrying anything around, and if I'm simply going on a random bike ride not carrying anything or picking anything up, hook it closed before leaving.

Last night I went on a short ride with the one basket hooked onto my left side to pick up some take-out from a local restaurant. The styrofoam take-out container fit perfectly in the basket, I guess they follow grocery bag standards. On the way home I carried the food and my 5 pound Fahgeddaboudit u-lock all in the basket on my left side and it didn't bother me that the load was unbalanced so that's no problem. And I like having the basket sticking out on the left forcing cars to give me a little more clearance. I actually felt safer with the basket sticking out -- something I hadn't anticipated. Props to Wald for designing such a great product and building it in the USA.