Had to do more searching on what porexan is. Looks like it is similar to what we call styrofoam. If you had it in a sheet, rather than a ball, I think it would work temporarily as it will crush down. We were making the assumption that it was a much firmer material - sorry. As it sounds like you may need to do this for some time, it seems that padded boots would be a lot easier for everyone involved.
Sorry, having a senior moment: what are the EQ boots?
Jan 2005, RI