What's limiting concurrent nfs reads?

Hi

We're running an nfs server on a 2.4.21 kernel (SuSE 9), and our linux
clients are mounting using autofs4.1.4. Quite often we'll need to
access the same file on the server with 40+ clients. When this happens
we'll only get around 20 clients mounting using nfs (the rest will
mount using smbfs, as my automount script supports both). I upped the
number of nfs daemons to 16, but this didn't make any difference. I've
done a lot of searching, but I can't find where this limit might stem
from.

Any help would be appreciated.

Cheers
Andrew