Billk, You should be able to build suitably sturdy shelves 30" deep, but access could be a problem. It is better to have all trackwork within easy reach. Typically no more than 24". But of course this is determined by the height of the railroad in relation to your height and reach. The lower the railroad, the further your reach will be. Or, if there is no track in the 6" from the wall you won't have much reason to have to reach it after scenery construction. 30" would require hefty construction, I would think. I have built 24" shelves in the following manner: I screw 2x4's to the wall studs, starting about 6" above the baseboard heating and to within 1 1/2" of the bottom of the subroadbed. I then place a 24" long 2x4 on top of the 2x4 stud on the wall, extending into the room. I cut gussets from 1/2 plywood, a triangle with the sides coming from the right angle 12" long. When screwed in place, these gussets give the bracket the strength it needs to support the loads it will carry during and after construction.
Gary
