Bear in mind that the marks tend to come from mounting and unmounting. The recommended devices, allow you to remove the tripod and leave the plate attached, but then... you have to leave the plate attached, and you have this quarter-inch +/- metal wart on the bottom of your camera that gets in the way when you flip it vertical to use the grip. So if you are like me you will then remove it when you are not taking a tripod, and will still get some rash from attaching/removing.
They are a MUCH more convenient solution, and worth it if you use a tripod much. Just saying, don't expect to never have a screw touch the bottom again, unless you leave the wart... plate on the bottom.