The majority of order pickers have a base width of 40", measure first. My suggestion is to match the platform with the machine it will be used. The idea emanates from the recommended direction of travel is with the operator in front, the load in the back. These are generally narrow aisle applications and the last thing you want to do is crash into the racking. If the platform is wider than the machine, it's hanging out where the operator is less likely to be able to see, can you say snag? Likewise, the operator will be further away from the units they are picking.