Your explanation in post # 41 does not say anything about the BigOppDetail. Change it to include this table so that its purpose is clearly defined.
Now we are talking about opp types? Do you see how confusing it becomes? That is why you should call them by two completely separate names and don't ever refer to them as anything else. A house contains rooms which contains doors - these are all completely different items and no way can they be interchanged. Begin to think in these terms.I am thinking these two as separate opportunity types