After being bounced around by the wind on the interstate, I decided to try my luck with a windshield.  I got the M-100 by Motoplex out of Canada, brand name Road Krome.  Clear plexi, 15" tall.  Got it on EBay for $70 plus shipping.  It's marked DOT certified, and installation was a snap, except that they left out 4 nuts and I had to improvise a bit.  I picked that height because I had read that the best height for a windshield was about mouth level, and it seems to be good for me. 

I found that wind noise was pretty bad with the first mounting position, but experimenting with different angles seems to minimize it.  Right now it's almost vertical, quietest position so far.  It does a good job of blocking the wind.  Almost no bobble-head  , even behind a big truck.  I wear earplugs when I ride anyway, so the wind noise isn't that much of an issue for me, but might be for others.  As long as I'm wearing earplugs, I'd rather have the low-frequency wind noise than have my head buffeted.

- Ben
'90 GS500 E

As far as i-state speeds, I try to avoid it.

But...

I have a little flyscreen that is just a stock oem SV650 screen, and it gets the wind off my chest. The line of 'clean' air is actually right at my neck, so the helmet isn't buffeted unless I'm behind an 18 wheeler, and that is a good sign to back off a little.

Post some pics of your setup. Maybe someone has a similar screen they're thinking of purchasing.

Ride on, ride SAFE.