The Spitfire is definitely a nice looking screen, I had one on a Rebel 250. But for the Zuma I just went ahead and got the Yamaha screen. It's ugly, being basically rectangular, but it seems to do a pretty good job. I noticed my GPS speed actually increased a couple mph with it on. I would have expected the opposite.
I won't spend more on a bike than I think it's worth, but if it's a good deal, I don't seem to have a problem buying bikes I don't need.
2002 Vulcan 750, 2013 Royal Enfield B5
2001 XT225, 2009 Genuine Stella
1980 Puch moped