I lurk daily, looking for ideas and resolving questions I may have with my layout (which is still stuck between my ears), when I had my garage moment. My reason for life made me sell our house that was almost paid for, to move closer to her job, which paid more than mine. In the deal, I got over half an acre for dreaming up my logging line (plus a commute of 110 miles a day, not that I am bitter) and a 20 by 30 garage with a nine and a half foot ceiling. I think I got the better deal because I always imagined that my railroad would grow outside and I would part with my collection of the lesser scales (some of which I have been collecting for 50 years), but reading indoor threads gave me my garage moment. I figured that I could build an indoor "test" track in the garage, incorporating a 20 by 30 oval with eight foot diameter curves. Then my garage moment multiplied to a garage five minutes. It struck me that since I was indoors and I had my narrow gauge ladies, Connie and Annie, turning my head, I could utilize the lesser scales along side my large scale. I doodled a track plan, which looks sort of like an op art figure nine, and if I have learned anything here it would be to add 10 foot minimum curves (thanks guys!), which wouldl really make the lesser scales look good as well. My reason for life gave me a gift certificate for Home Depot, which I will I will use for material, I figure 1/2 inch OSB for substrate and 2 by 3's for ceiling supports. My question is how much space should I allocate for the g scale track, HO, and N scale for the substrate? From the wall out, I see large to small scale, but have yet to settle on a width. In addition, I have had moments where I add my O27 Lionel into the picture along with a slot car track, but I think that is a ways off yet. Going back to my question of width, since I am well over eight feet off the ground, does the width of my substrate eliminate the need for a guard rail (or cable)? I am giddy with anticipation.