I recently did the CE wing on my ice cap GR. I used a little anti seize on thoes foam washer/gaskets to transfer into the painters tape. I also drilled out the plastic on the inside panel of the hatch then 3D printed a plug that snapped into the drilled hole for a clean factory look.
Hey! You're back. Was wondering where you'd gone off to. I'm tempted to make my own wing. I'm not convinced that any of them provide substantial downforce. Especially when I see that they're mounted to a plastic hatch.