All I can think of is pulling the fitting through the tile hole, tightening the outlet on then squirting silicone in the hole and pushing the outlet against the tile till it sets?
Just realised I should be using something like this:
I know it should probably be a backplate elbow but other than mashed up brick in the back of the hole there's nothing to fix one to. If I secure this in place with tile adhesive and or silicone so it's just back from the front of the tile and loctite 55 the thread it should hopefully be ok.
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