In defense of the sharpmaker on this, I have been using one on my old swamprats without any damage to the convex edge. In fact, at a 40 deg angle, the rods only are touching the very edge of the blade. Very little comes in contact with the rods at all. The benefits of a convex grind are not compromised. I love my sharpmaker. Keeps my D2 bog dog so sharp it will take the hairs off a flea's back. It also can get my battle rat much sharper than it needs to be as a big chopper.
Just my 2 cents.
-Brendan