My home-made lucite windshield is just about 3" above the upper end of the side bracing arms from the fairing. This makes the wind hit me just above my sternum. I like the wind in my face but off my body, so this suits me fine. 4,000+ miles on it and still going strong.
No heating was necessary.
If I were to make another today I would use my Dremel with a plastic cutting bit (looks like a drill bit) for the cut.
Also, don't pre-drill the screw holes. Get the lucite on there, tape it down and drill the lucite with a metal bit, or a plastics bit if you have one. Start in the center, put the screw in when you have drilled your hole, and work your way up either side.
I do plan to drop the fairing by 2" vertically and put lower bars on the bike. I plan to paint the fairing and bags to match the bike.... when I paint the rest of the bikemaybe next summer though. My concentration right now is on my 78 CB750F Cafe project.
Here is a pic of the fairing on my K6 (it was on the 78 F previously). It's hard to see it in the photos but you'll get the idea.
