.aac Dolby 2.0 audio volume too low

I'm looking for tips on working with Dolby 2.0 .AC3 compression. It seems that after I encode the audio, the volume levels are slightly reduced on the final DVD. My mix hovers around -12db in FCP and I've set dialog normalization (in Compressor) to -31 (and -27 as well.) If I bring in the original .aif file into DVDSP and drop it in one track and place the .aac asset in another track I can here the difference in volume when I switch back and forth in the simulation. This is very noticeable in the final dvd because I always seem to have to crank the TV volume. Any tips?

Kevin