The weight of the shoe might be a problem, so perhaps some kind of treadmill type solution would be more feasible. I find loose sand to be tough to run in and

The weight of the shoe might be a problem, so perhaps some kind of treadmill type solution would be more feasible. I find loose sand to be tough to run in and kind of frustrating with the whole running through molasses feeling. In one running book I have (Running for Mortals) it recommends flat, firm sand only but does call it a "treat for most runners". The same running book lists these surfaces as being worst to best for running on in terms of bodily stress: concrete (e.g. sidewalks), asphalt, dirt paths and trails, grass. However, because of convenience, I run on sidewalks almost exclusively and I seem to be able to pull it off so far.