I should point out, that even though during the hotter months here I ride with the slanted back, cut down stock shield, I also have a 23" Parabellum shield that is not too bad with the stock mount for cooler temps. I managed an 1800mile trip around CO this summer with it, and didn't complain...
I had the exact same problem with the stock windshield. I cut mine down about 5-4 inches and it still didn't help. I installed a madstad bracket, and that only helped a bit.
What I finally ended up with is using the madstad, but I look off the crossbar and leaned the screen back far enough to...