Thanks, guys.
They're not O-72. Almost all of the layout is O-36, so I tend to run smaller steamers and diesels, which is fine with me and is like having an automatic spending limit on my engine purchases.
The curve around the roundhouse is O-48, which makes it look a little better.
The Lionel LC 2.0 + engines are actually designed to run as low as O-31 curves, which I think is great for people with smaller layouts who want to run bigger equipment and don't mind the excessive hangover.