I opened up the taillight on my '68 7ECA and the inside bore of the fixture is a little less than an inch, plus the fabric wraps around the lip of it and down into it. There's discussion of opening the bore of that fitting with a grinding bit but I'm on the fence with that option.
What about those slots? From the second link, it sounds like something slips through those and then you rotate to lock?
Welding a new receptacle is not a big deal at all - it needs to be steel, and should probably be .064 or heavier. A good welder can do it in five minutes. Takes me twenty. Maybe uAvionics should stamp out a few?
I forgot to check. Been busy with a wing repair. Will try to remember manana.
Sep 25 - forgot again. Was heading toward the rudders and got distracted. Blue Angels close our airspace all day the next three days - I will tie a string around my finger - should have plenty of time.
Sep 26 - same deal. Jets over my hangar - distracting.
Sept 27 - I remembered! My J3 rudder has a plenty big steel thing, and I had necked it down with wood. A rasp opened that right up.
The Decathlon has a skinny stamped affair - a 1.08" socket will slip right in the outer opening - a 1.12 socket won't. There may be enough metal left after grinding, but better to weld in a new receptacle. I bet Steve Pierce will have a few cut out of good steel, and a really good welder could stick one in without much more than an inch from weld to fabric.
If your fabric is nitrate/butyrate, use shaving cream on the fabric. Take the rudder off to do this.
Sadly, I put those sockets on top of the caliper case, then put them on the truck cab roof. Calipers wound up in the bed; sockets have not been seen.
We will be getting the first tail beacon this month, for a Super Cub. I will be doing the grinding, and another IA will do the installation and setup. Full report in November. Plus, I will grind the spare decathlon rudder, then test for remaining strength. I think the stamping welded into the rudder is identical for Cubs and Champs. Probably a Grimes part.