you can do it either way, as far cutting first or not. I mark where i will glue the riser on and then taper the limbs up to that point, then i cut 45s off each end of the riser. Once glued, I sand the fades down into the limb and then tiller from there.
You must not be cutting a shelf. I have not made but a couple shoot off the hand bows so your dimensions seem short to me. Remember either way that if you splice the two, that it will be shorter (don't mean to insult your intelligence, but i mention it because i have overlooked the obvious before)
since you went end to end on the two pieces, i would add another piece over them, it would be a contrast and insurance, you could add a "handle overlay" for more than cosmetics, and it would not only round out your grip, but stiffen the joint