Like you, I really disliked the mousehole, especially since the silly little flappy cover kept falling off on the road. I took an even easier route to a solution, though not as elegant as yours. On my 2006 2720SL, the inboard end of the cord was (and still is) secured inside the left bumper compartment. I simply pulled the entire cord, including the plug, back through the mousehole and into the bumper compartment. Once inside, the cord is easy to coil up in the compartment, and is deployed directly out of the compartment, rather than through the mousehole. And it's easy to uncoil just the length I need to reach the power post.
http://www.trailmanorowners.com/foru...pictureid=1975
As it turns out, the center of the coil is just the right size to store a 20-amp-to-30-amp dog bone adapter, plus the hold-down weight for the sewer fitting, making it handy as I push the fitting into the campground's sewer riser. That weight is described here
http://www.trailmanorowners.com/foru...ad.php?t=13615
And there is space for a battery cutoff switch next to the coil.
Now, how can I use that open mousehole?
Bill