I think Spar is okay for card magic, but probably too soft for card flourishes.
Thanks for your nice words on New Fan Back.
When I placed order at USPC for New Fan Back decks, I made it very clear about the few problems that I encountered with some of their decks. At the time, some of their decks were totally unfannable (black seal Tally Ho, green arrco etc...), or too thin (rider...I think they still are very thin these days). I remember I was shooting for a DVD with a newly opened rider deck, I ran through my patter while holding the deck in left hand dealing grip, when I back into action, the bottom card already magically bent on its own!
So I requested specifically for thicker paper stock and finish to make sure New Fan Back are fannable, springy and ideal for card flourishes,
and I wish for a hand feel of Dr. Leon decks.
I was very nervous about the quality of the decks until the several randomly picked decks from different grosses all fulfilled my expectation.
Still, the hand feel are slightly different between White and Black New Fan Back...so I come down to a conclusion about this, even USPC themselves couldn't duplicate the exact hand feel of their particular deck.