I don't think remaking just the head would work. The entire setting (donut and prongs) needs to be taller in height. I used to own the WF Tiffany setting and it was just so short and low set, much lower set than the real Tiffany solitaire. A taller setting + snugger fitting eternity might do the trick.
I agree with you! I think the whole head needs to be redone which includes the top part... is that the shank? So yes... I agree... it's not just about making longer skinny prongs.
@CharlotteYork You may want to also measure how tall the top part of the shank is... that's the 3.23 you see in my other photo.. experts.. help.. what is that part of the ring called?
That part is hard to measure as it is angled, and I kept coming up with different numbers, but I agree with @Laila619 that it is more than just the actual "6 prongs". It's the whole head that needs more height.
By the way, I am 100% sure WF will know exactly what the problems is. I would think since they do custom all the time, they can figure this out in 15 minutes with their tools and not leave it to guess work.