Chris,
I probably will invest in the book, hopefully I can get it at my LHS without having to wait to order it on-line. If necessary, I can use a smaller switcher for yard operations, but you are correct regarding the utility, or lack thereof, of the SE track. I haven't really thought of maximum train length. Right now I am content with a maximum of three plus a loco and caboose. I am hoping to be able to go at least another additional car on this layout. As for car length, I prefer the shorter ones, no more than 50', and probably 40' for most of them.
I admit that I spent all of yesterday working on several different designs, based on every other book I have already accumulated, including Westcott's 101 Track Plans.
The layout size is dictated by the room size, obviously, and quite frankly, if it weren't for the fact that I now have the model RR bug, this layout is taking up more room than I originally envisioned.