You can tint the full windshield, just not "legal". If you go with light enough tint, most cops wouldn't even realize. I have 35% on my whole windshield. It's noticeable, but so far haven't had any issues.
As for doing just the top portion of windshield down to legal ASI line, I can't stand the look. Looks like they forgot to do the whole thing, and after riding in a Ram a couple weeks ago with the visor tint strip, it would annoy the hell out of me while driving. Maybe if it was a gradual transition from clear to dark it wouldn't be so bad, like the factory one was in older cars, but the sharp edge is just too much and I felt myself wanting to duck down to see under it.