As Breeze said, there is no single, correct answer to your question. Many, myself included, have literally spent hundreds of dollars searching for the perfect shield. The proper height shield is one that you are still looking slightly over the top of so I'm convinced you can never eliminate 100% of the buffeting. I'm currently using the 8 1/2 Clearview with recurve and it's pretty close to perfect for me.
You may also want to install a fork baffle and some fairing side air deflectors before throwing any more money at the actual windshield. These help a lot!