It's not just designing the formula, getting the parameters right is going to be a right pain. You might have meant that as part of "designing" but it's a sign

It's not just designing the formula, getting the parameters right is going to be a right pain. You might have meant that as part of "designing" but it's a significant challenge in its own right, over and above having a formula that's the right shape. Not to mention numerical accuracy in the implementation, but I'd assume that's mostly known patterns at this point.