What is the advantage of using veneers when building fiberglass bows? Also, what thickness is used?

the advantage is LOOKS and about .025 will work

So---an osage veneer will perform the same as an oak veneer?

Most commercially made veneers are approx. .020" thick.  When used on both the back and the belly the total of .040 needs to be taken into consideration when figuring draw weight.

I am no bowyer but as Ric said I know it effects weight but I doubt performance. Shawn

I have heard more than one bowyer say that black glass shoots a little faster than clear glass.  I don't know.  I am sure it's not a difference you could see.

IMO veneer don't add much performance to a bow , what you have inside and out side of it make a bow what it is.
that being said,lets hear from the rest of the bowyers out there

Like Ric and Harold said,they are for looks.The core lams and design make the performance.A bow made of ,say, all bocote laminations wouldn't perform as well as one with red elm or boo core and bocote veneers.JMHO