live constant link to MySQL table on web host

[Rothko]

It would seem this is something that should come up quite often, but this part of the fmforums isn't too helpful about it. Maybe because it's obvious? Anyway, here my question:

My client needs their local contacts database synch with a MySQL database. They have a form on their website for people to subscribe to a newsletter. The newsletter mailout happens via a PHP script on the backend of the website.

The client might also enter some contacts locally into the FMP database, and some of those should receive the mailout too. So the two databases should really be one, not least because they might overlap.

I have no experience using FMP 9's new External SQL Data Sources, but according to what I've managed to find I should be looking at a live link.

The FMP part should be rather simple, almost a flat database of just one table. But I'm concerned about speed and responsiveness, especially if more than one user accesses records.

It's a small office with max 6 users accessing the database at the same time.

Has anyone got experience of this kind of setup? Am I going down the right route here?

Many thanks.