I have a 12 x 7 space in a room adjacent to the train room where I'd like to stage long trains (30 cars - 2 and 3 engines). I'm giving thought to a double track helix going down 3 or 4 loops and a single track loop within that coming back up. I'm trying to maintain 32 inch minimum radii. I need it run flawlessly so I don't have to switch rooms to re-rail, etc. I've never done a helix and wonder what the usual things to watch out for are and I'm requesting feedback on the concept of a helix within a helix. Thanks.