I have not -- yet. But I think I am getting fairly close. I have this frame solidly clamped in a vice, and am taking pretty good swings at a removal-tool with a 5 pound sledge now. One cup is out, and the other is moving, but still has a couple millimeters to go. The removal tool just gave up the ghost, however, as it was unable to withstand the impact.
I am becoming concerned about the damage that I may be doing to this frame, which was probably not designed for these impacts. I suppose I will find out if it cracked when I sandblast off all the paint, which is the next step. Will have to check it for bends, as well.
All I wanted to do was re-paint the frame -- I wasn't trying to perform a destructive test on my welds.
Clamping the frame in the vice ensures that much of the impact is being transmitted through the frame (which is acting as a spring) and is thus being absorbed by the frame and the vice.
Take the frame out of the vice, and have a helper simply hold the frame up loosely - grabbing it through layers of shop towels or the like, to ensure that the impact force isn't being absorbed anywhere but at the point of contact - and tap the the cup out gently (while moving the point of impact a few millimeters at a time) with a blunt punch or screwdriver or whatever tool you can safely adapt to the purpose.