Major bug: Audio Levels incorrect on export

Here's what I'm trying to do and the frustrating results I'm getting. The idea (and the client's specs) is to export a ProRes file with discrete audio channels. 24 in my case each being a discrete mono track. We've been doing this in FCP7 over 4 years now without any issues. When trying to replicate that same workflow inFCP X, I get incorrect results. So I ran a quick test to see if FCP X is messing with audio levels on share or export for those of us who deliver to the gazillion providers other than YouTube.

In FCP X, I import a mono (not stereo or dual-mono, just plain mono) reference tone at -20 dBFS. My project is set to surround (this is for multichannel projects).

In the timeline it plays at the the correct level" -20dBFS and all looks and sounds good. My file is 24 bit 48kHZ so is my project. I also have FCP X being monitored through a Videotek for measurements.

The imported tone is measured and confirmed to be at -20 dBFS on the Videotek, as well as in Audition CS6; straight from the file to eliminate any patch cord speculation:

I assign a role called TONE to the audio clip and export role as separate file.

With PAN MODE set to NONE and channel configuration set to MONO I get an exported audio file that is 2.67 dB quieter than my original file.

So I try a different approach: I set PAN MODE to Default and channel configuration to mono. I get a file that is 6.02 dB quieter than my original file.

So last try: I set the channel configuration to CENTER and the PAN MODE to NONE. I get another file that is 6.02 dB quieter.

The logical outcome even with pan laws in mind, should be: you import an audio file at -20 dBFS, you verify that the audio levels are correct with the audio meters, you export it and you get an identical -20 dBFS audio file.

I do this all the time in FCP7: you set your audio channels to mono and set the pan law to 0 dBin your sequence settings. done.

So what is going on in FCP X? I know a whole bunch of post houses deliver files for broadcast. Do they all have these incorrect levels? Or do the editors compensate with a gain of 2.67db or 6.02 dB according to the audio configuration. Which mind you is unacceptable because if the FCP X meters say my reference tone is sitting at -20 dBFS then my exported file should be -20 dBFS not some arbitrary number.

I ran this test on multiple machines: MacPro Mountain Lion 10.8.2, Macbook Pro ML 10.8.2, MacPro Snow Leopard 10.6.8 and I get the same results.

Anyway, I'm really suprised that on this board I only found a handfull of threads that mentioned this issue. None had any solution or explanation for this behaviour on export. Yet, it is a pretty serious one. Am I not doing it right? But then I had other people try on their own and they are reported the same thing.

Any light shed on this issue would be most appreciated. Until then, FCP 7 and Pro Tools are my only hope.