Yeah, I'm realizing now that I should have explained in more detail. Here's my slip:
We're bow-in, with a finger to starboard that separates us from the boat next to us. On the port side, there are only bumpers separating the boats. It's hard to see in the picture, but there are pilings that, when we're tied in, are just aft of the transom.
When we started to back out, after all the lines were off and "out of the way" (or so I thought), we actually slid the boat back by hand out of the slip. It wasn't until the bow was about 2/3 of the way out of the slip that I started to put the boat in reverse, and it was at that point when the line snagged the fender.
BLJ, I've toyed with your solution. I have read your comments on this topic before, and you make some valid arguments. In the end, though, I like the idea of having my starboard spring line set up and waiting for me as I enter. I've docked here twice now, and each time I've managed to grab the stern line instead of the spring line, but I'm going to add some color to that line (or replace it with a different color line) so I can distinguish it more easily. The theory is that I'll come in slow (I drift in), grab the spring line off the piling and throw it over the mid-ship cleat, then let the momentum snug us to the dock. I attach the starboard stern line while I'm there, then jump off and connect the bow lines, then back aboard for the port-side stern line.
Like I said, that's the theory...so far, I've grabbed the stern line both times and come up WAY too short in the slip. Thankfully, it's easy to fix and much better than if the stern line were too long.