Prusa Top Spool Holder

I have been using this http://www.thingiverse.com/thing:45930 spool holder and happy so far. However, I need the spool to be on top. After some searching could not find a suitable one so design this. This is a spool holder arm designed to sit on top of Prusa top parallel bars and using the same spool support from http://www.thingiverse.com/thing:45930.

I intend to make this beefy, 7mm thick to hold 1-2 kg of spool; and some holes to save material and look nicer.

This works with regular fil