Dave, I haven't thought a lot about the cassettes, but I did at least think that I need sides and ends so nothing rolls out and there needs to be padding. I also thought of using two handles that would go around the width for stability when moving and be able to slip off once in place. I will do the testing with inexpensive cars. I don't know what I'll make the handles of, but that's good enough for now.
You are right, I wouldn't need a wye switch for the branch with only one switch. No, I won't be racing for sure! I usually run in the teens or low 20s mph as shown on the DCS remote. You do have a point about turning into a switch going down. Thank you for pursuing the idea of the extended loop.
I agree with you about trying to get more level track. First of all, it is easier to build, but also we are used to seeing railroad track that usually looks flat even if it has slight ups and downs. Whenever you get the chance. There is no rush on my part. Today, I moved my sections of benchwork as close as I could get into place. I don't know if anyone has noticed, but there is a fireplace with raised hearth on the long brick wall at about the place we have the upper portion of the passing siding. I will have to cut one leg off 11" from the bottom and that leg can rest on the hearth. No worry, the house is 51 years old, and the fireplace has never been used. It is really a very bland looking fireplace, so we won't mind covering it with the layout. Oh, the top of the opening comes right to the bottom of the Mianne cross members, so It can be accessed if need be. (Accessed by a younger man than me is my idea) 
Thank you!!
