So here is my tip for square grinding. I have a Simington swing arm. I have never bought a square ground chain and have only converted round ground chisel to square. I always like to use the gray waxed wheel for converting chains over. You have to remove more material when converting chains over and the gray waxed wheel will not burn the cutter like a blue, white, or salmon wheel does. I have done Picco, .325 and 3/8ths without any problems. I believe someone mentioned on here making the wheel a little thinner. For the smaller chains that is what I do to keep out of the tie straps.
If I am going to touch up a chain then I will use my blue wheel because it will hold the shape for much longer.