Maybe I am confused... It seems like it would be easier to just raise the saddle by 1mm to produce the same effect? There is an oldschool method of setting the action where you increase the height at the saddle to where you don't hear a buzz and then lower it until you do. Then raise it back up just to the point of no buzz.*

*You want to make sure that your nut height is OK. Do this by capo'ing at the 3rd fret and making sure you can slide a piece of paper between the first fret and the string.

If I do that then the strings are very high off the fretboard.
The thought is that if the neck was in a 18mm socket, then the angle would mean the string is just a bit higher off the end of the fretboard, but not correspondingly higher off most of the fretboard (given that the nut is also lowered).

Capo'd at the 3rd fret - there's room for a thick piece of paper and a credit card.

I've done the "spot" levelling... it's a little bit better again.

I'm thinking that perhaps I was too worried about taking off too much from the higher frets (after taping at the 9th or 12th fret).