I have the 26" Woodmaster Drum Sander and have installed the reversing switch for the belt. I would not be without it.
If you setup and the "cut" is too shallow, without the reversing switch you have to wait for the full board to feed through, deepen the "cut" and try again.
Or if it is too deep, you can reverse before you damage the full board.
It is just generally handy to have and with the small cost of the switch I wouldn't be without it. I mounted mine up near the top on the left side of the machine for easy access.
Don Dando