In reply to Peter's question in #17 above I would not expect any damage to the outer spring boxes from the diamond hard chroming of the inners. It will be important that the inner spring boxes are well polished before plating so that the chrome is on a smooth surface, otherwise I do not think there is anything to worry about.
Now, #20 above; there was a lot of thought that went into the design of the JE system and the range over which the wheel moves is controlled by the front damper. I do not know how the dimensions of the Thornton unit compare with the AVO one. All the tests and measurements which I did were with an AVO unit without oil, even to the extent of having a scale on the outside of the damper and another on the outside of the inner spring box, just to measure where the limits were. I do know that one person raced a twin with a JE front end used a Thornton and found that it handled so well that he did not feel that he needed a steering damper. That is until he got into a tank slapper, after which he fitted a hydraulic steering damper and possibly reverted to the AVO. Just make sure that the front wheel spindle movement is upwards and backward for the whole of its travel.
Now, #20 above; there was a lot of thought that went into the design of the JE system and the range over which the wheel moves is controlled by the front damper. I do not know how the dimensions of the Thornton unit compare with the AVO one. All the tests and measurements which I did were with an AVO unit without oil, even to the extent of having a scale on the outside of the damper and another on the outside of the inner spring box, just to measure where the limits were. I do know that one person raced a twin with a JE front end used a Thornton and found that it handled so well that he did not feel that he needed a steering damper. That is until he got into a tank slapper, after which he fitted a hydraulic steering damper and possibly reverted to the AVO. Just make sure that the front wheel spindle movement is upwards and backward for the whole of its travel.