Gonna do something like you did re towing loops. You've got two bolts into the frame and your loops are (I think) about where my bolt through the frame extensions are. I think you said ground clearance on that was about 4 1/2 inches? How's it working?
I ask because my idea is to use my bolts as the rear support and the jack points as the front, with the towing loops just in front of them, maybe 2-3 inches higher off the ground (and easier to reach) than what you did.
But before I get started I want to learn all I can about flat-towing Spyders with homemade towing rigs. And you're the only guy I know so far that's done it!