[Qrr]

''For some reason I though radar did not reflect well from just the fiberglass or "plastic" and most of the reflection was due to the engine block and a bit from the windshield.''

And you are absolutely right .

The main secret ingredient in the stealth paint is graphite .
To absorb a specific frequency they can mix graphite + nano particles of metal , the formula is really secret . But you can assume that graphite is a broadband absorber.

A fine powder of graphite is obtained by filing a used electode utilised in electrolysis plant/plating or buy at a very specialised company. Your difficulty will be to incorporate this powder into foam or use a latex paint exterior and add as much powder in the paint and litteraly coat the inside of your bumper , the ticker the better . Many coats = better .

Now ...is it effective ? By all the books/publications I read over the years =Yes . By which percentage it will diminish your Rcs (radar cross section) ? ... unless you have a very sophisticated lab to test $$$$$$$ ...or do test with a real radar before / after ...and tell us the results.

Stealth is the future.