Hi Frank, the 22 foot length will give you some room for a very long run. Will you be able to walk completely around it or will you have it against a wall. Seven feet is a long way to reach. I have a set of the 21 inch lionel passenger cars, my outer loop is 54 inches, while they run on those curves, they don't look that good. 60 inch or 72 inch would be the way to go. The 7 feet would be 84 inches so one outer loop with 72 inch curves would work. Having a second layer would be a nice feature. Its kind of a pain to connect the upper and lower loops, so you can just keep them independent. It would be good to put a list of features you would like to have, like an engine house, and yard tracks. With the amount of space you have, running five trains would seem reasonable. I can run three trains on my 12 by 12 layout, while there are switches between the loops, I never use them, I just run them and keep a eye for derailments. You could have two of the loops connected for switching activity and moving cars around.