I submitted a support request at Rally Armor, asking about the OEM Splash Guards, Do the OEM parts come off, or are they left on when fitting the Rallyarmor parts?
Rally Armor wrote, We recommend that you remove the OEM guards prior to installing our Rally Armor mud flaps.
I ordered the Rally Armor mud flaps and found that the OEM guards must remain installed, both front and back.
A few other things I found might be useful. The attached photos show the rear Rally Armor mud flaps installed over the OEM Splash Guards.
1. The OEM fender-edge clips have metal nuts and use machine screws. The OEM machine screws are plenty long enough for the extra thickness of the Rally Armor mud flaps and the associated large-diameter plastic washers.
2. The OEM fender-edge clips are MUCH more secure than the Rally Armor equivalents. I used the OEM parts.
3. The rear Rally Armor flap is very loose at the inner side, being supported only near its top. I added a large-head-diameter sheet-metal screw through the Rally Armor flap and into the lower, inner edge of the OEM Splash Guard.
4. Although Subaru appears to have added a drain slot to the lower, inner edge of the OEM Splash Guard, I removed one, and found the outer side full of dust and dirt. The Forester had only been on been on pavement and good gravel roads. I think with normal back road use, the Splash guards would fill with dirt. I therefore added a ½ drain hole on the lower, outer edge.
5. I found the Rally Armor plastic clips insecure. The plastic parts strip with no apparent increase in torque from what it takes to just advance the screw into the clip. It was good to find that the OEM clips and machine screws on the rear fender lip work well. If you are installing Rally Armor flaps on a 14 lacking the OEM Splash Guards, it might be worth a trip to the Subaru dealership to pick up four of the Subaru clips and machine screws.