I've just built up an oldish Handjob for the missus and whilst doing so noticed that the edge of the internal hole in the headtube (the one that's visible when you look down the headtube) is only about a millimeter from the wall of the top tube on the inside.
The weld is intact and I can't think of any reason why 5mm of overlap is different from 1mm but it just took me by surprise.
No pictures I'm afraid but appreciate any advice.

If the frame was built that way then I'm sure that Cove knew what they were doing.

i'd imagine that 99% of the weld is on the outside/contact surfaces

Cheers.