The variety of possible configurations is staggering.

Start with the face of the plug. What's best - flat, concave, or convex (how about a cone - never have seen one of those)?
Then there's the length of the flash hole channel flame channel - 1/4", 3/8", 1/2" ?
How about the diameter of the flash hole channel - .035, .030, .025 ?
And the diameter of the flame channel between the primer and the flash hole channel - 3/32", 1/8", 3/16" ?

If one selects a flat face, is a larger flash channel better than a smaller one? Would it be the same with a concave face?

Someone please - select the best of each and design the perfect plug for us.