Mate you may not have to sell it!
I had a UO 2x barlow which i believe is identical. It wouldnt allow focus seated all the way in but did if lifted up about an inch or so off its shoulder. I used a posties rubber band on mine to act as a stopper once i worked out the correct height. Give it a try.
http://www.iceinspace.com.au/forum/a...se.php?a=56026