I bought a set of SKS commuter fenders, not realizing they're slightly different than the Chromoplastics (also see here: SKS P35 Black Fenders 700c/35mm. The commuter fenders are actually not even listed on the SKS website. They are about $10 less than the chromoplastics if that's important to you. Here's the package:
The commuter fenders most importantly appear to be shorter than the chromoplastics, mounting hardware aside. They mount a little flimsier than the chromoplastics as well but I haven't noticed any undue side effects from this. However, the length of the fender is somewhat problematic.
As you can see they do not extend far enough to cover the rear wheel to the point where spray won't cover your rack and equipment on it:
I decided to extend the fender using some rubber stair tread bought at Home Depot and whatever I had on hand, in this case the carrying strap from a car battery.
I cut off one of the notches that slot into the battery to allow me to thread the strap underneath the fender (to make it look prettier in the end):
Using a drill I drilled a hole in the strap the same size as the stock opening on the fender, this is about 17/64:
This allows you to use the stock mounting hardware to fix the strap directly to the fender. Note that removing the stock mudflap will give you the room to fit the mounting hardware, just be sure to trim off the excess plastic from the drill hole:
And put back together:
Note that at this point in time you can choose to mark/drill a second set of holes on the other side of the metal clamp, then use whatever fastener you have to secure it in place. Just Make sure the fastener isn't long enough to start rubbing your tire. I chose to simply zip-tie the strap to the metal bracket for expediency. Note that the entire fastening area will be held well away from the tire, even with only the one metal support because the metal support is attached to that bracket. So it's far less likely you'll produce something that'll start rubbing the back of your tire in this manner.
Here it is, fastened back on the bike, note where the metal support is relative to the end of the plastic strap:
I cut the stair tread to make a 2.5 inch wide flap, I would suggest making it longer than mine, perhaps 12.25 inches:
(continued in next post due to image limitations)