I have a cutlery set of steak knives, carving etc..from RADA. Great products and the RADA sharpner puts a razor edge of all knives.
I used it to touch up my Zwickys and Snuffers, brought them back to hair shaving sharpness. I tried it on my Schulz Hunter heads, similar to the HH heads but the ferrule a tad thinner, got them sharp but not razor sharp like KME got them.
I don't think Howard Hill ever got those heads shaving sharp. The large ferrule makes it tough to get the right angle with a file.