I agree w/Normandy, 12" seems reasonable. Another factor is that some PRCs are built with a 4 degree forward tilt - meaning the leading edge will be lower to the floor than the edge closest to the operator. Add to the fact that due to the extended load centers involved, weight of the attachment and load weight plus diameters to 96" + - the forklift will "baby buggy" some what while traveling over less than perfectly smooth floors.