Received my new tires and tubes yesterday, I ended up ordering the Michelin UHD tubes - 4mm thick and natural rubber. If I had seen ATDCT's comments first, I would probably still be dithering over what to buy. It seems everything is a trade off with this bike.
Now that they're here, I'm going to spoon them on as soon as the weather gets warm enough. Put the new tubes on the scale, and the rear tube weighs in at 4.6 lbs. I'll weigh the old tubes when I pull them out to try and get a sense of the weight difference.