Thanks for the info. As long as a screen can remain in place, if I ever see one of these locally at a reasonable price I might grab it.
For now, my three-bladed Kenmore multi-directional box fan does a fairly adequate job in both directions. I place it in an upstairs sash window opening and can feel the air flow from it as I go up the steps. I have a small window A/C unit in the adjacent window for those hot days when the upstairs gets entirely unbearable, but can almost always switch to a fan at night. The heat issues are much less pronounced downstairs, and fans are usually sufficient.