Thanks jcl.
Some things may be finally sinking in.

Your dice example helps, and should probably be added into the manual.
I'm still not understanding a few things, though...
Why is the 0 profit square root rule used rather than the + profit rule? Because the square root rule is more pessimistic?
If the Test period was, f.i., 3 years, why isn't the square root rule already accounted for over an equivalent Trade period, and kicks in after that?
Shouldn't Test match Trade? IOW, if I'm planning to take out Income, shouldn't the Test be run with those removals? This would change DDs, etc.
Let's say I have $15k to risk on all this. Is it more risky to run, say, Z12 on one account with the entire $15k? Or 3 Z12's on 3 accounts with $5k each?
Re. the 2nd question, all of this applies to WFO and such Trained and Tested strategies, correct? Aren't Z4/5 by nature different and all profit removable?
Thanks.