trigger TOASTing quicker?

Hi all,

I'm in the planning stages of replacing a MySQL DB using ISAM tables
with PostgreSQL 8.1.x on Suse 10.0. I think that sentence right there
will tell you why!

Anyway, one of the columns in one of the tables is a big chunk of XML
(500 to 500KB). I'm not normally a fan of that kind of thing, much
preferring storing such things in the file system. But I see that
TOASTing that column will address most of my concerns. On to my
questions:

TOASTing is automatic? I don't have to code anything for it? Plain
vanilla SQL99 will work with it? I have terrible memories of Oracle's
LONG RAW columns....

Assuming the above is true, is there anyway to get a column's data to
TOAST at a threshold smaller than the default of 2000B? For example, I
really would like any amount of data stored in the XML column to be
TOASTed. So I would like to be able to say something like
ALTER TABLE foo ALTER COLUMN xml SET STORAGE EXTENDED;
ALTER TABLE foo ALTER COLUMN xml SET EXTENDED_THRESHOLD 500;

tia,
arturo