How thick or thin is your riser sight window (A)??
The riser has two 1/8" phenolic strips
(B)= 2-1/4" and closer to the top of the sight window it's 2-3/8"(where it starts to curve back)
(http://i1293.photobucket.com/albums/b593/osagemark/100_0492_zps8d6081bd.jpg) (http://s1293.photobucket.com/user/osagemark/media/100_0492_zps8d6081bd.jpg.html)
I like mine about .750. With the bulge you have opposite the widow and your accents .750 would be plenty. Of course you know to radius your corner where the window and shelf come together.
Yes on the Radius
my riser are 1.4 wide and I go Half way .700
I thought they could be thinner
Just checked my 2 personal bows, .550" and .650"
One has a lot of phenolic in it and the other has 2 pcs of glass and 3 pcs of wood in it...
Like Mike said .750" is safe, and less flex(which slows the bow)
That spot to left of arrow in top pic is the weak point, corner of sight window to thumbrest.
Radiusing like Mike said helps...