what is the aluminium grade and thickness of the adapter in the last photo? (the thickness of the single stepped part, not overall thckness)
without going back, I think I saw mention of 3/16 " = 5 mm or so - is that going to be strong enough?
I have made rear brake adapter from 6 mm aluminium, not sure of grade but judging by colour is plain raw aluminium .... but looking at disc brake adapter ansd drop out, these tend to be 8 mm to 10 mm thick so my one may not be strng enough (I am in process of making another out of 8 mm).
These are 7.5mm thick in cross section made from 6082 aluminium, the same thickness as the AMP drop out. They can be annodised, but this would cost more obviously. Just being in contact with oxygen, aluminium will form an oxidized layer on it's surface.
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