I wouldn't use OSB for the driveway because it is heavier than plywood and soaks up water. You can screw handles or straps onto the platform so you can move it more easily. I used 3 layers of treated plywood. The extra layer of plywood feels nice. If you use short screws you can screw the middle layer to the bottom layer, then the top layer to the middle layer, then the stall mat to the top layer. I just used treated deck screws. You can always just move the rack instead of the platform. Coach's plans are excellent, BTW.