Yes, they can supply a reinforced clamp mounting for exactly this purpose. Ambassador Marine - Accessories for the Stripper Propeller ProtectorSpeak to ambassador -surely they have faced issue before?
Rotax, do you have a picture of your DIY sleeve? Were you happy drilling holes through the P bracket? And I can't find a commercially available S/S slotted sleeve.
Vyv, Ashtead, I spoke to Ambassador. Their clamp won't fit as the leg of the bracket is coincident with both ends for the tube carrying the cutlass bearing ....and they don't have a sleeve version.