Also, remember that "reach" can be affected by the weight of what's being reached. You may be able to reach 36" to re-rail a boxcar, but your shoulders may scream bloody murder if you try to reach that far for a 12 pound locomotive that needs to be re-railed. Finally, the further you have to reach, the more likely your body will damage something at the front of the layout.
If you kept your width to 24," you have another advantage in construction cost because you can get 2 pieces of 23 and 3/4" inch width from a 4x8 piece of plywood.
