I don't think there is any need to over think it. I made beds out of the "small stuff" from the creek. It mostly ranged from sand sizes to 1 inch pieces with some rocks up to baseball size. The majority of this gravel was flint-like, some jagged, but some smooth. At any rate, I just grabbed some from the creek and made a 15 by 15 foot area for spawning and the first year out of the gate they made beds. I will admit that I have seen no evidence of YOY, but my fish were HBG and 3 to 5 inches long at that.
I will say that if ewest says "Mixed road gravel a little bigger than pea gravel is best." then it's the best.
