So I am new to model trains. Have known a few people that have had very nice setups and always loved to watch them run. Anyways to the point. I have a O gauge train I am trying to set up a specific was for the holidays. I essentially am going to have long curve that I want to loop and double back at both ends. So my idea is I will put a switch on the end, and I want it to loop back into that same switch but going the other way. Then when it gets to the other end, I will have the exact same setup thus creating the constant loop.

My question is: I already have two of the O36 Manual Switches -Left Hand, (one for each end) so if I am using an O31 curve, what additional pieces will I need to complete the loop back into the switch. I am also open to using an O36 curve however I was trying to make the turn arounds take up as little space as possible. But if the O36 would be significantly easier to do, then I will sacrifice the 5"

If someone would kindly be able to post the additional pieces I would need I would greatly appreciate it. Also feel free to let me know if doing a O31 is a bad idea or not possible at all. Thanks