UA listing question

Hello,

Would someone be so kind as to answer this listing question for me?

I have purchased a business class zed tix for LAX-LHR and LHR-LAX on UA and backed it up with a coach zed tix for the same trip in case I can not get into the B cabin because of SA (This is specfically allowed by company rules and the UA interline agreement BTW). The question I have is that while the rules say you can purchase both a Bus class and a coach class zed for the same flight, it is not real clear on listing. I know I have to list online using the I90 system but should I list twice? Once for B and once for the Y cabin? Will this tilt the system? If I only list for the B class and I cant get in there will they auto rotate me into coach and then allow me to use the coach tix? I dont want to use the B SA fare to sit in coach when I have a Y SA tix in my pocket. Of course this assumes I can get on the flights at all.....Does any of this makes sense?

Thanks!

Since no one answered I am assuming no one knew the answer. So, in case others have the same question, yesterday while at the airport on another flight, I contacted a CSA for UA who had a moment and asked about it. I was told that you only have to list once in this situation. If they can not get you into the C cabin, they will roll you into the Y cabin and you can use the Y tix. Then you can save the c tix for another time or turn it back to the company for a refund....