When building a magazine platform for a specific cartridge what formula do you use.

I'm aware of a formula for magazine dimensions but have never seen one for magazine platforms.

I'm of the belief that a cartridge specific magazine platform could slick up the feeding of about anything.

If you mean the magazine follower, I don't use no formulae; I take one already made for that caliber, and copy that. Its is not just the follower, it it the relationship to the magazine box as well. For example, I have made .404s feed well from a standard width 98 box, and made them feed from wide custom boxes. Different followers.
Everything has already been invented.