I quibble.
(perhaps erroneously)
Palindromic means that the place notation to dodge the treble, say, in 3-4 up is the same as the place notation
to dodge the treble 3-4 down.
There will be a pivot bell, it will make the place at the half-lead, and be symmetric about the half-lead.
Cambridge is palindromic.
Plain bob is palindromic.
Bristol has a stronger form of symmetry.
It's a double method.
So the place-notation to dodge the treble 1-2 up (5ths, in this case) is the mirror of the place notation
to dodge the treble 7-8 up. (4ths).
(And as you correctly say, if you flip the line in the mirror and translate it a half a course, you get
the same line. So point 4ths lead point 4ths for seconds place bell around the halflead, or
point 5ths lie point 5ths for the end of 7ths place bell, lead end, beginning of 8ths place bell)
[Superlative is also double.]