Never had much luck with x-ray on anything without a decent gap. Especially when welding in place on the bottom portion. 6G position with TIG, the gap was critical as need to insert rod through gap and actually "hold" the puddle up with the filler rod so stringer bead did not sag and be below flush. The fish eye you are referring to I suppose is the same thing we called a "keyhole" when running stringer bead on alloys like chrome, inconel, monel and titanium pipe. Basically, you hold the torch where the arc is breaking down the bevels on each side and the rod is fed above this "keyhole" opening whild the weld filler metal flows off of the rod, around the "keyhole" and deposited on the backside of the "keyhole". If you feed too much filler, the "keyhole" closes up and the bevel stops breaking down. Only solution is to stop and grind the gap back open. Stick welding 6G can use tighter gap and when heat set right, pretty much all the "fire" is on the inside of the pipe on stringer bead. Sometimes, TIGing sch 5 stainless, when we could roll them out, would fit tight with minimal land on the bevel and could fuse the joint dragging a 3/32 rod for filler ahead of the puddle allowing just enough extra metal to flow off the end of the rod to flush it out before running a cap. Always use argon purge on alloys or inside of stringer will "sugar". Different metals have different weld characteristics and need different techniques to make x-ray quality welds. Hope this helped a little.
