I think you may be asking the impossible impractical, Simon
Have you compared the thickness of a half 5BA nut with the pitch of 4BA ?
MichaelG.
.
P.S. Skimming down some full nuts to a realistic height might be the best option.
Edit: David beat me to that ^^^
Edited By Michael Gilligan on 26/03/2019 10:05:57