Not to hijack the thread, but another alternative are XC Racing Flats. These are designed for races from 5k up to a marathon. I bought an inexpensive pair of Saucony flats and total weight for the pair is 13oz. They can be had for as little as $30 on sale on the Web. Lighter brands are available, although at a premium cost.
This type of shoe is designed to handle muddy/wet/slippery XC courses, grip the foot to be secure in turns, have minimal impact on feet such a blisters, and provide some support. Also, work well with just a sock liner or even sans socks.
These can actually be used for UL hiking (I have done it on good trails), but won't get you much life out of them in terms of mileage. Just an option I have not seen anyone explore.
Typically I use them as camp shoes when doing desert hiking that requires hauling a lot of water and wearing boots, or when hiking in areas that are very wet such as canyons with mostly sandy bottoms. For me they are a specialized piece of equipment that I do not use very often... but am glad I have them when conditions are right.