When bouncing a mono file to disk, you many encounter a 3.5dB increase in the signal. This is a result of bouncing a center-panned mono file to a mono file. There currently are two workarounds: 1) disable automation and pan the source track hard left or right before bouncing, or 2) decrease the level of the source mono track before bouncing. The upcoming Digital Performer 2.6 update will have a separate bounce to mono with 3.5dB option.