Noticed the dents on my donut spare a few weeks ago. Last Sunday I checked and the full size spare has dents forming as well. I ordered a 1/8" thick sheet of abs plastic and cut it to size to act a as shield. Let's see if this helps. Will check again in a month.
Installed mine today. Took about 5 min per guard. Hardest part for me was pushing the larger middle rivets in the rear (2 per side). If you don't want to remove the rear wheels you need a stubby 5/16 drill bit for the lower 2 rivets. Video explains all of this, fast forward to about the 18:30 mark.