I agree with Bubby. 1 3/4" to 2" should be about right. I think rounding the fades as you suggest should work out fine. The grain on the face looks just fine to me, but I'm curious, do the growth ring lines run that straight on the edge of the board? If you back it with rawhide, it shouldn't matter much, but if you have run-outs on the edge, leaving it unbacked could be a problem.
Edit: make-n-break beat me to the punch.