Thanks for the info.
I had another thought... the sole purpose of the self-levelling mechanism is to do away with the traditional method of gluing into the key cup a flexible, leather covered, felt and card disc around 4mm thick. Once glued in this has to be manipulated by heating the glue again so as to level the pad face with the rim of the tone hole which is drawn from the brass body of the sax in manufacture and then levelled. So the traditional method has variables: the glue melted into the key cup would have to be level with the inner rear surface of the key cup; heating it again when assembled could throw off this level; pulling the pad around with picks could twist it from being flat.
But... once done the slightly squidgy pad would have no tendency to move from level with the tone hole rim other than, when squeezed hard at its leading edge under finger pressure, to compress more at that edge and then spring back to its original shape when released.
Remember, the pad only has to level once, unless there is some accidental movement from a knock or other intervention. In this case, the pad would need to be re-settable but this will be rare.
So, assuming my pad material, at 1mm, is thick enough to allow for the increased compression at the edge furthest from the pivot point (around 50mm further than the nearest edge which is 20mm from the pivot - someone do the maths!) what I need to do it to let the pad self-level, then remove it and apply a locking liquid, then replace it, press the key lightly to level it again, and let it set. Then, when squeezed hard the metal to metal locking fluid would resist any further movement as with a normal glued in pad.
I'd still need to be able to unglue a pad by levering it out so it needs to be something like a removable thread locking liquid, or a rubberised glue (a little movement may be advantageous so long as it springs back again, or even a contact adhesive.
So, from allowing maximum movement I'm suggesting the opposite so as to stop the front of the pad lifting and not self-levelling completely due to the friction at the pivot caused mostly by the strong magnet. The pivot has to have enough friction to move so as to self-level but not enough to flop about when the pad is in mid air. I think that sufficient friction to achieve this is also too much for the pivot to change with tiny inputs which change its angle ever so slightly.
What "glue" will bind metal to metal lightly but also be separable? It needs to give me around 30 seconds to install and level before it starts to dry.
Thanks for your help!