LM 4 Tweaks vs. NR 6 Changing defaults

[Graham Percival]

It's time to start discussing what to do about tweaks and Changing
defaults in the NR.

LM 4 Tweaks has a lot of explanation about tweaks.
- do we want to duplicate all of this, in a condensed form in the
  NR?
- should we just move LM 4 Tweaks into the NR to avoid harmful
  duplication?
- if we have other material to explain (like how
  #'break-visibility works), should add this to the already-large
  LM 4, or add it to NR 6 changing defaults?

At the moment, I don't have any particular opinions about these
issues.

Cheers,
- Graham