We did the same for LH458 MUC-SFO tomorrow. But J is sold out and we are currently 1&2 on the UG list. Doesn't sound too promising.

ETA: 3 hours before flight, ticket agent said we were now 2&3. Not sure if any additional UGs were released, but we sat in the back. Will send in the unused certs and try to do it all over again in 4 weeks.