I can honestly say ive never seen an ipe, unbacked bow.  
By the way, congrats on the bun in the oven.
"zeNBowyer  
I  see  IPE  sets  a fair  amount "
Usually, IPE has very little set.  I can only assume the light weight of this bow, plus the touchness of ipe with out a backing, is what created the set.  I get very little set at all with Ipe.  I love the stuff for that reason.  Plus the density.  You can make thin bows with ipe due to its density.