Bluray output exceeds 25gb - no adjustment possible?

I need to create a blu-ray of a 2-hour feature film of mine. But using the built-in "bluray" "destination in FCP, the output = 27GB. And a normal BR disc is 25GB.

The video encoding, unfortunately, (in compressor and as used by FCP) is "LOCKED." If I could lower the bit rate from 30Mbps to, say, 28Mbps, the film would probably fit. However, compressor will not let me make any changes to this preset. Therefore FCP cannot do this job, even though it's "close." For the record, I have made much shorter blu-rays successfully a day or two ago.