There were only a few people building 1-1/4" head tube frames at the time and of those, only Yeti would supply a FTW stem and fork with a frame. If you were to claim I welded this frame, I would not argue your point. If another builder claimed to make this frame, I would not argue their point or your point.
very nice work BTW.
WAIT! Lets see that seat post clamp... It looks like a Yeti part. We had our own post clamps made from a BMX extrusion for our 1-1/8" seat tube diameter. If that same clamp was modified to fit a larger aluminum seat tube, it might have the problem you describe.
Removable pillar clamps were a little unusual at that time also.
sorry to keep bugging you like this.