You can place washers under the black plastic windshield frame to shim it out. If you want to lower the top edge and lay it back some, put the shims under the bottom two between the steel subframe and the black plastic frame. If you want to raise the top edge and move it away and more upright, place the shims under the top two bolt areas.
Some have gained enough drop to see above the shield just by shimming the bottom two bolts.
Shimming the bottom also allows more air under the shield, reducing the Vacuum effect some.
Plastic, brass, aluminum or stainless steel washers work best, no rust. If you never get it wet then common steel will work fine. The most you can get with the factory bolt is about 1/4 inch. Any bolt distributor/vendor has longer bolts and washers so you could add enough spacers to hang the shield out 4 inches if you wanted too.
You will need some new well nuts if you are going to play around with this. I bought 20 off Ebay for like $14. Thats 5 windshield changes. You can reuse well nuts but they crush up when you tighten them and are hard to get back in the holes again. I have done it in the past, just double the time fiddiling with those little nuts in tight spaces.
I know this works on the 650 and many other bikes. I do not know if it works on the 650 Exec or the AN400's. Others will have to answer those questions.