fire polishing a 10mm piece
Flip and fire will give you the crisper lines and it will round. There are some things you might consider.
The rate of advance needs to be slow, not more than twice your rate of cooling from the annealing point. Faster and you risk breaking the piece on the way up.
Depending on how long and at how high a temperature you use, the 10mm of glass may begin to flow. This tip ( http://glasstips.blogspot.co.uk/2010/04/prevention-of-needling-in-dammed-box.html ) will give you guidance on how to set up a dam to keep the piece from expanding, but without getting needling on the top edge.
Make sure the surface that was on the shelf is very well cleaned. I sandblast mine to make sure everything from the firing is cleared away. Without a sandblaster, very thorough scrubbing is required.