Be careful how you bid regarding passover pay
Like you, I was hired as a 727 s/o. I short time later they started hiring directly into the 727 f/o seat and assured us that we would be eligible for passover pay. I short time later I upgraded to DC-10 s/o.
At my year anniversary I expected to see the 727 f/o passover pay (I think it was higher than DC-10 s/o pay?). I didn't receive it ... when I called to find out why, I was told that I did not have 727 f/o on my last bid so I was not entitled to the passover pay. I asked where this was written so that I could verify this information for myself. I was told, "It's not written anywhere, that's just how we do it." ( I thought that was a bad answer and felt as though I had been cheated!)
If I were you I would write both my ACP and the payroll people with your understanding of how the systems works. If they write back that your understanding is correct, you can probably take that to the bank. I'd figure that they are not likely to put themselves on report after they emailed you what you wanted to hear (after all, you have it in writing now!).
I don't recall reading anything in the contract on the subject, seems like an oversight to me.
Hope this helps ...
Regards,
Mark