I'll be tagging along on a trip with my wife next month SFO-FRA-ARN and back, where I need to book separately to get on the flights she's been provided by her job. SFO-FRA is LH 455 (LH metal), whereas FRA-SFO is UA 901 (UA metal).

Having eked out enough miles to qualify for 1K this year, I plan on using a paper SWU to try and upgrade the SFO-FRA segment (she's already booked into C - lucky her!) This thread has been immensely helpful in understanding this process. It does leave me with a couple of questions, that I hope those with experience using these things can answer.

1. While there seems to be some dispute, my understanding from reading the entire thread is that the paper SWU can be used as long as the plane is LH metal, regardless of whether it's booked via LH or as a UA codeshare. I've also seen recommendations to book under the LH # to play it safe, however. If I book the trip through UA (on the phone, to ensure a V fare class on the outbound), will they only be able to book under the UA flight number? Or can they book the LH # for the outbound, and the UA # for FRA-SFO, so I can (attempt to) confirm that upgrade in advance?
   
   
2. I've seen advice to check in online 23 hours in advance to help one's standing on the upgrade list. Does it matter whether one has booked the flight under an LH or UA flight number? (eg, can I use OLCI for a UA marketed LH metal flight at either lufthansa.com or united.com?) My concern here is that if I book with UA as a code share, I won't be able to use OLCI. (That said, I'm not _that_ far from SFO, so I could BART down there whenever check-in opens and do it in person if need be.)
   
   
3. The 'I should know this' question: I don't think I've ever flown a TATL code share. I take I check in at the LH desk either way if the flight is LH metal?

Thanks in advance!