Dave, I think you are right! 8 inches will work okay, because like you say, I'll just store alternate consists there. I'm not much for making up and breaking down trains like some of the series operators are. On the other hand, I want to do more than just run trains in circles. This plan will let me do that. I can figure a way to keep other consists on cassettes on shelves like John suggested.
One last note on the laundry. I took off the two brackets that held the heater shelf above the dryer. Then I put the first spakling in the holes from the lag bolt holes. My wife said she really likes the shelf and window panes gone. I think that confirms it.
