That was the initial idea. Its just that some people on TL.net were saying the second overlord will give you +8 supply added to max, and thus is useful. This means that it shouldn't be considered as a loss in minerals, as it serves a clear purpose (essentially, not a replacement, but a gain). I soon discovered that isn't guaranteed, and can be anything from 0-8 supply added to max depending on unit production. It took me a while to work that out, as Im not a maths wiz.
You only lose 8 supply from losing an overlord, so the worst case scenario that you are at 50/50, you would be brought down to 50/42. This means you are guaranteed to go back to 50/50 after building 1 overlord, and if you build a 2nd overlord, you will have over-compensated and gone up to 50/58.
Rebuilding the overlord you sacced will put you in the same position you originally were, and this only costs you 100 minerals.
I also noticed you keep mentioning that you 'lose 100 minerals when the overlord dies', this isn't true since the mineral 'loss' doesn't come from the unit dying. I think this is where you might be double-counting because you are considering a loss of minerals where there isn't one.
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