Made a bit more progress, the liftgate is done and operational. I also installed the protection panels on the side to keep fingers out of the cables. I had to ad-lib a bit on mounting the protection panels, they had a pretty lame design that only supported them from the sides. This is a 48" span, so the Masonite was flapping in the breeze. I added some wood blocks and supports to attach them on all four sides. I just used some old scrap lumber to space them out to the same plane as the legs. I'm hoping the extra blocks on the bottom I-beam help support the liftgate, all the weight of the liftgate is on those two 4 foot I-Beams, makes me a little nervous. The Masonite panels attached top and bottom and the blocks are helping support the weight on the bottom I-Beam, hopefully the liftgate lives a long and useful life.
The only remaining task for the liftgate is to add controls to operate it from both sides, the single control isn't going to do the trick. I saw a couple of Internet solutions, but I have a little problem with them. If you parallel two switches across the connections for the single switch on the control, it all works UNTIL someone on each side flips the switches in opposite directions at the same time. Then you get fireworks! 
While that's a remote possibility, Murphy was an optimist, so I'm not taking any chances!
Here's my latest update, the completed and operational liftgate. 
