I've seen it done on a short scale instrument without any problem, so a medium scale should also work, as long as you are able to recreate the neck relief lost by the lower tension of the Piccolo strings. You can easily experiment by lowering the tension of your existing strings and adding neck relief with the truss rods. See what the truss rod range is on your instrument and that will give you an idea how low a string tension it can handle. Make sure you are comfortable with this simple adjustment (there are several discussions on this board on how to do it, like Joey's Post on Setting Up Your Bass under Must Reads, etc.).