Originally Posted by akl_traveller

Thanks for all the feedback. I've realised for this I'll need to build a process model with variants and then work back from this to the equation.

After consideration, I won't attempt to factor in lost luggage or interrupted trips. They'd have to come in as very low probability modifiers to expected benefits and as such I doubt they'd influence the final decision making model at all. Low frequency, high consequence events worry humans, but maths handles them more soberly

I will also be assuming a hard 7kg limit to carry-on, as that's the commonly stated limit and assuming greater capacity strikes me as cheating.