Do a trial booking with a fully refundable rate and by right, after you make the reservation on the confirmation the 2nd person charge that you saw earlier should be gone. It is listed when booking initially, but if you are AMB or RA is gets removed during the reservation process (final step when you confirm).

Silly feature how this is implemented, but at least the second person fee always vanished in the past for me. Should it not, with a flexible rate, you just cancel and no harm done.