Thanks jcl. But I don't think we're on the same page. I understand between versions there are potential discontinuities and the formula can't be directly applied. However...

Q1: While running a given version and not upgrading to a different version, I wish to reinvest profits. Since I'm still in "linear land" since I haven't changed versions, the formula applies, correct?

Q2: If the above is correct and the formula applies during the time period of running a given version, what do I use for OriginalMargin after an upgrade(s) has occurred?

Going back to the example numbers and expanding the example:

I start Zx 1.17 with $1k because it Tests to CR of $1k for Margin 50. Zx of course laugh does a wonderful job and balance rises to $3k. Since I'm still on 1.17 I apply the linear formula and get a new Margin of (say) 75.

Now 1.32 comes out. Following your prescription above, I Test 1.17 at Margin 75 and come up with CR of (say) $2k. I run a bunch of Tests on 1.32 and find that Margin 103 gives CR ~= $2k. So I upgrade to 1.32 and set Margin to 103.

1.32 does even better than 1.17 (of course laugh ) and after a bit my balance is $10k. I want to reinvest profits. Since I'm still running 1.32 and in its "linear land", the formula above applies - except: What number do I use for OriginalMargin?

Q3: Or, if the "linear land" formula becomes completely invalid after any upgrade, what formula do I then use to compute new Margin for reinvesting?

Thanks.