The size only takes affect after a certain volume level at certain freq is reached. So for your normal conservative listening level, you could in theory even set it to MAX. But then you would have to switch it back and forth depending on whether you are in cinema or music.

Also, for movies, with your setup, you are not getting the bass from the center speaker. I think even if you set your center to small, DTS will still send a full range signal to it. So you might have to sum up the LCR channels to get the full movie effect. Also, moderate listening level for HT means nothing, since there is a tendency for the studio to add something real real loud to the center channel frequently, the always want to go near that 0dBFS for no reason.

I asked Meridian for some chart or graph that correlates between size/freq/dB, but they don't have any. They said just to play freq sweep through the speakers and set the size right below the point where the speaker distorts or bottoms out (I think I might distroy my speakers in that process, cranking sweeping sine waves at such loud level for so many continuous passes.)

I have a 5.0 setup with sub for center and sub for L&R, all actively crossed over at different freq for speaker and sub. I left it at MAX for now, since DD/DTS automatically limits the max LFE to -5dBFS, but on some situations, I measure 55v peak output from the sub amp, which works out to be >750w, over the amp's 500w spec, and the output was not 100% clean. I might one day do the above freq sweep/size adjustment if I don't mind taking the chance of blowing up the sub and/or amp.