5: https://i.imgur.com/3BQKZrm.png

Wow that was a great leap to Rebus. I wouldn’t have guessed in a million years that it was already constrained to 1.

Technically the last move is always a forced move :) The effective part was getting rid of 'E' in the 4th slot, leaving U as the only available vowels.

I was surprised though that there weren't any digraph-based solutions even though I still had S and H in.