About your cord extension plans..
I've done this thing before with no problems. The hardest part is finding the five wire cord. But I used a cord from a beat up coil I had in my spare parts.
This is what I did.
You'll need the basic's or a soldering gun w/solder. And some shrink wrap tubes, small ones to cover the small resoldered wires, 5 about a inch long and two larger shrink wrap tubes large enough to cover the spliced areas, I made them around 5 inches long each.
Clip where ever you want to put the extension but I made it a foot from the coil. Put on one of the larger wraps over the cable and push it down the cable and away from where your splicing. Expose the five wires inside, clean off the coatings and leave enough to solder to the other cable your using for the extension. I made them 2 inches with about 1/4 to 3/8 an inch for soldering. Before you solder put the small shrink tubes over the five small wires and push that away from the soldering area and any heat. Solder the wires together one at a time and push the wrap over each and shrink as you go. If you want to retain any shielding, you can split it a carefully fold it back and rewrap it on the cable.Then I used cut pieces of electrical tape and wraped the repaired area until it was almost the same diameter as the cable.
After that I pushed the large shrink wrap over the spliced area and shrunk it so it fit nice and tight. The process is the same for the other side of the splice. Rememebr to leave enough wire to work with on both sides.
Then you can remove the control box from the pole. I used a larger clip from a large tape measure but I JB Welded it to the back close to the orginial mounting holes from the pole but not over them. This way I could got back to stock set up with a different coil or wrap the excess from the extended one.
Actually, I've done this one three machines and I will do it again. I even made it waterproof so I could float the box and not fear any leaking at the splice. You can do this by also adding a clear flexible plastic tube as close to the diameter of the cable but large enough to go over the large shrinkwrap tube. Then I used quality sylicone I squeezed into the tube, I used black automotive. This way you can see the sycicone enter the clear tube and make sure it's completely covered. It's messy but you can wipe off the excess before it dries. For added protection you can use small hose clamps on each end. I used quatily nylon pull ties and they worked perfect.
If you don't have a cable with the same color wires just make sure that whatever the color is one one side is the same as the other.
I hope this helps you hipmount the 505 and gets her back out and enjoying the hobby. Happy Trails, Hunting, and Have a great 4th,
Woodstock