If I were that frame, I'd feel naked!
I agree about the 'Jammer and the 450 being overkill. But, in the era of the 1970s, it was also the only practical frame-mounted fairing: we were installing them on CB350 twins and CB350F bikes and more than 1 were on the Yamaha 350 twin 2-strokers in the college town where I had my shop. I saw one on a 305 Dream Honda, but he had to have made his own frame mount (and where?) as Craig didn't make the 'Jammer for any bikes smaller than the CB350 Twin and Four in those days. The Quicksilver was originally intended for those smaller bikes but it caught an edge into the "looks" category and showed up on customized bikes right off. That wasn't what was planned, but it built a niche that way. It's a nice fairing for guys like me who got tired of hanging onto the handlebars at [real] interstate speeds, which are now back again.
An interesting view into Craig Vetter: my Honda mentor Jim Chamberlain and he were tight, and when Craig made the first Phantom for the 750 he called on Jim for testing, who toured between central Illinois and his folk's home in upstate New York (in all 4 seasons!) on his Bridgestone 175 twin, of which Craig also had at his shop: Craig made the first Phantom for his own Bridgestone, and my friend Jim got the other one. There were only 2 of those, handmade, as prototypes for the Phantom for the 750. They were ridden for 11 months in all 4 seasons for testing: Jim went from Peoria, IL to upstate NY for Christmas Break in 1969, with that fairing. He came back and bought the shop's (where we worked) first sandcast 750 after that, and got Phantom #4, I think it was (Craig's was #2), as the fairing. Phantom#1 was broken up after the wind tunnel testing at the IL Champagne-Urbana wind tunnel showed it needed minor mods, leading the way into Craig's own. His 1972 Suzy waterbike became his own use of the Windjammer (I) we all know today, and most early pictures of him show that bike. He was said to have designed lowers for the Quicksilver, but only a few were built and sold, and I don't think his company made them. Talk about rare parts...