Walter,

The most important function of the glare shield overhang is to make sure that
a forward segment of the windshield is shaded from reflections off the
lighted instrument panel and your clothing at night.  This can be designed
with a cardboard shield, a shiny material simulating the panel, a flashlight
and a darkened work area with you sitting on simulated seat in the unfinished
cockpit.  Better yet, go flying in a finished IV at night and use a tablet of
paper under the glare shield to test multiple positions to see what you can
see outside during the landing phase.

There are many sun angles that can defeat any glare shield.  You will
probably get better panel shielding from the cabin structure.

For a rounded leading edge, I glued up a 1 inch by 1/2 inch thick piece of
foam on the aft edge of the shield and wrapped it with 2 layers of glass.  
You may want to make it thicker and consider adding wires and panel flood
lights located on the forward side of the "bulge".

Scott Krueger
LNC2 - N92EX - We live in a bubble!