Just wanted to report back . . .
I decided to go with the National Cycle Switchblade, 2-Up model. I installed it last weekend and, blessed yesterday with 70-degree weather, took my first ride with the new screen. It also was my first ride of the season.
I like the screen a lot. In 55 miles of mixed riding, including speeds to 70 mph, I had no difficulties with buffeting. The screen makes riding above 50 mph enjoyable, rather than the hang-on-for-dear-life thrill ride I'd experienced before.
It's only a first impression, but a good one.
My thanks to Chip for his help in ordering the right parts from National Cycle and for his installation advice.
Jeff