When I made my first osage bow I was making the transition from a glass laminated recurve to a selfbow and wanted my new osage recurve to have a sight window just like my Birhorn recurve so I cut the window shorter but just as deep as the one you have on your bow. I shot my new bow for a few months then "CRACK", it broke almost in two right at the arrow rest.
Since my first bad experience with a deeply cut sight window, this is as deep as I have cut one on the last 128 bows I have made. I took this picture of my favorite bow just now. I spliced several short copperhead skins together for the bow, you can see one of the splices in the picture. The arrow rest is not part of the bow but a piece of osage that I glued on a shaped.