Hi there
I took the U2 head apart with little trouble.
I secured the head in a vise with leather straps to protect the finish.
I heated the head slowly and gently but quite hot, with a hot-air blower (others have used a blowdryer- maybe a USL would work!)- this is the scary part as I am not sure if the HAIII could be hurt by this-mine clearly was fine!
This step is to loosen the Lok-Tite or similar that SF use.
Then I twisted the bezel off using a pair of multigrips with leather lining.
The whole thing took about 2 minutes.
Others have published this with photos- I guess you have tried a search!?
Good luck- I love my U2: imagine one with X-bin!!!!!!