This is a pretty short DIY, but I wanted to add it now that some folks are getting these extensions with their D-Specs.
1. Jack up car and remove rear wheels.
2. Remove two nuts securing the dameners at the top of the rear wheel wells. Use a 12mm socket.
3. Compress the dampener by pulling down and pull toward you once free from the studs. I secured mine by letting it extend against the outer part of the wheel well such that I could access the hole easily.
4. Using a 1/2" bit, drill out the smaller of the two holes viewed within the shock mount hole. It should be the smaller hole that is closer to you (or exterior of the car). Be careful when drilling to keep the drill from 'jumping' far into the hole just when the drilling is nearly complete - you run some risk of damaging the rear panel cover. This can happen when the ears of the bit just break through the other side of the hole and catch on the metal. Just be sure to keep the drill steady as the hole is nearly complete and be ready for the snag. Although I didn't do this, you may want to install some tape, etc about 1/2" down the bit to act as a stopper.
5. Install the extension onto the rear strut and secure using a 14mm wrench.
6. Insert the extension through the 1/2" hole you just drilled and allow strut to seat in its appropriate position - DO NOT secure the two nuts just yet. You'll want to make sure the extensions routed themselves correctly first.
7. Fold down rear seat.
8. Remove baby seat Latch cover and plastic shroud. The shroud is removed by lifting up the rear (there is a lip on the back side) then slide it forward over the loop - this will make sense when you see it.
9. With a 12mm wrench, remove the bolt that secures the latch loop.
10. You should now be able to reach down through the latch hole with 1-2 fingers. If you reach toward the front of the car and slightly toward the exterior, you'll feel a layer of insulation. If you get underneath the insulation, you should feel the extension. Pull the extension end up and out of the Latch hole. If you don't feel the extension here, it may not be in the correct position. You may need to pull the dampener down and repeat step 6.
11. Adjust dampener as you wish - from inside the car
12. Replace plastic Latch shroud and cover.
13. Replace nuts inside fender well to secure dampener.
14. Repeat for other side.
15. Replace wheels and lower jack.
16. Enjoy your new found convenience!
You may find it easier to get the extension routed if someone is inside the car at the same time, but I didn't have that luxury when I installed mine.
Also, I may go back and notch out the plastic shroud so the adjusters stick up a bit more vertically like Dovla did here:
Thanks Dovla and James from CreativeAutoworks for your advice!