Thanks jcl. We're finally in agreement on a lot of things!!! laugh

I thought the correct answer was c) too.

I agree with not using a formula(s) one doesn't understand - that's why I keep asking... laugh

I also agree with saving backtests - especially now that they take so long, esp. for Z12. frown

While I understand the method above, it's even more so too cumbersome now given the latest Z12's Test times. Can't the rule of 3 save us?! laugh We don't all have unlimited budgets to run on Tianhe-2, aka Milky Way 2... laugh

So, my (perhaps final laugh ) question is: Can the rule of 3 be applied as follows: Run backtests only once for the new version to find the Margin setting that gives the original, starting CR. Then apply the rule of 3 using that NewVersionOriginalMargin?

In the example above, run backtests to find NewVersionOriginalMargin = Margin on <new> version that gives CR=$1k.

Then, whenever one wants to reinvest (while still on that same version) no backtests needed! Simply rule of 3 calculate NewMargin=(CurrentCapitalPerSquareRootRule/OriginalCapital)*NewVersionOriginalMargin.

This seems to me to apply the rule of 3 as if no earlier versions existed and only the new version had been run since starting. Is there some reason this doesn't work?

Thanks.