Phil,
I did the same type of mods a number of years ago on my old Nomad th'er. What I did for a connection point on the door/ramp was drill a couple of holes on the extreame metal edge of the ramp and connected a couple of beaners to each side for connecting the cable. Then I connected the upper beaners to the point where the springs attached to the frame. I don't know if this is possible for you as I'm not familiar with your ramp setup, but anything's possible (especially with Howie).
Good luck,
Clark