I'm surprised that you don't have that kind of screen real estate.  24" monitors with 1920x1200 pixels are quite common now.

I just did some playing with non-preview mode.  Kinda-Sorta ok. I can arrange the folder view as a vertical strip on the left, then a center list view, then a right message view.

The biggest problem is that on many lists I don't read the msg sequentially, so I end up with a huge number of message windows stacked on each other.  Since you don't have a "close all message windows", I have to click the close button on each of the dozens (or more) of the message windows.

I've also noticed that if I double click in the list to open a msg, then decide to double click on another msg in the list to open it - it doesn't work.  I have to click, wait for focus to change, double-click to open another msg. (remember, non-sequential reading.)

I see you do save the "last opened" size/position for each of the msg list windows, so I'll just have to manually position and size each of the 200 or so lists I have.

Sure would be nice if there was a pre-defined 3 column preview format.

Is there any way to get the Preview pane on the right?  I have a wide screen, and the view layout wastes about 1/2 the screen off to the right.

Putting the preview on the right, and the msg list in the middle makes a LOT more information visible at a time.

Afraid not. If you have that much screen space spare, perhaps you could try changing Pegasus into Non-Preview mode by clicking the 'List' button. You may find that being able to have several windows open at once is a better use of the screen for you.