I've got my SG mounted to the windshield with a gooseneck suction-cup bracket, positioned left of the steering wheel and just above my left hand with hands at 10-2 on the wheel.
One problem with that is, if the sun is out I'm either getting glare from the sun on the SG, or seeing reflections of myself/traffic/whatever on the screen. Makes it next to impossible to read it easily most of the time. I've got another bracket I built that mounts below the dash, no probs with glare there but I stopped using it because I have to take my eyes too far off the road.
So I came up with a very cheap quick fix that doesn't involve building any kind of "box" over it to block the light. Thought it might be useful to others.
All you need is a roll of scotch tape. And optionally, an x-acto knife with a
new #11 blade.
You want the tape with the "matte" finish, not the "shiny" finish. Clean the window on the SG thoroughly, let it dry then pull off a piece of tape slightly longer than the window. Put the tape on the window carefully lining up the edge of the tape with the top edge of the window. Use the back of your fingernail to press the tape down onto the window, working carefully to eliminate any bubbles.
Once the tape is on and smoothed out, go try it out. If you don't like it use the extra bit of tape left on either end to peel it off. If you
do like it, use the x-acto to trim off the excess. Use the "back end" of the #11 blade (the end that goes into the handle) to carefully work the tape down into the corners and along the edges, then
carefully cut the tape along the edges of the window. Peel off the excess so that tape is left only on the window.
Believe me, this WORKS! I can shine my 3-cell Mag Lite directly on it and there's no glare or reflections at all

The only downside is the display is not quite as sharp but the difference is very small and it is a LOT easier to read it in bright sunlight. Hope this tip will be useful to someone!
DH