> matter of taste: how much
> transparency, and how much permeability, do we actually want?

Yes agreed.  If I really end up wanting to do it, I'm sure I can write a build
method for them in a subclass.

I was mainly just wondering whether there were any "system" reasons or caveats
to doing it.  I guess I'll find out if I try it..   :)

> Is there a particular usage of #instVarAt:put: that you're thinking of
> that you'd like to have caught?

Just one at the moment but its probably no big deal..  To change a value in an
inspector and Command+s.

Thanks,
  Chris