You may want to set the Dialog Normalization at -31, instead of -27. The 5.1 on the SE laserdiscs is already reduced in average level by 4 db compared to the 1993 and 2004 mixes, and leaving the DialNorm at its default value will lower the volume even more. You can always turn your receiver's volume up more to compensate, but I think it's better not to have to do that. The simple trickery of DialNorm reduction is one of the things that fools people into thinking AC3 isn't as good as DTS, because they think the dynamics are being compressed even though they aren't really. Setting it at -31 will mean that the average levels are unchaged during playback.
If there is a Dynamic Range Compression setting in the encoder, I'd recommend disabling it, otherwise anyone without a surround setup will hear a significantly less powerful version of the soundtrack, since Dolby Digital decoders always force the use of DRC in anything less than a five speaker layout. Only top of the line Denon models can bypass this that I'm aware of. (This is another thing that makes people think AC3 sounds worse than DTS.) If you must use DRC, keep it at a light level to avoid compromising the sound too much. Laserdisc 5.1 tracks had no DRC applied, because the only people who could even access them already had surround systems to begin with; but foolishly most dvd's choose to rely on the player downmixing instead of including a dedicated 2.0 track as the default, so the sound is watered down for the benefit of people watching through tv speakers.
The center and surround downmix settings of -3 db should probably be left alone, because I think this is to make them come out correctly when put into matrixed Dolby Surround. However, I'm not sure about the 90 degree phase shift setting. This probably also is intended for optimal downmixing, but I don't know what effect if any it has on normal 5.1 playback.
Make sure your channels are in the right order. As listed in the window, AC3 wants them to be left, center, right, left surround, right surround, LFE; this is different from the typical multichannel wav layout (left, right, center, LFE, left surround, right surround).
Optionally, you might want to try using the 3 db surround attenuation setting for ESB and RotJ. Now I don't know whether it's a technical fault or intentional, but to me the rear channel effects in the SE's are way too loud for these two movies (not so much in ANH, though). It could have to do with the difference in calibration between large theatre mixing rooms and small home theatre variants, or they might have just mixed it that way on purpose--I don't know. But when compared to the 1993 mixes through Prologic II, the difference is very obvious, and the '93 surround levels seem much more appropriate to my ear. You could experiment with that and see which you prefer if you're so inclined, or just leave it alone and adjust the levels in your receiver, or not bother at all; it's up to you. ;)
