Recommended value for max-cache-size for cache-only shared hosts..

[blrmaani]

We are planning to use cache-only BIND configuration on our hosts.
These hosts are shared hosts i.e BIND runs along with other
applications on these hosts. RAM size on these hosts = 8GB and hard-
disk size=500GB.

Question:
what is the recommended configuration for 'max-cache-size' for optimum
usage ? I was thinking to use the default value of 32M.. any
suggestions..

thanks
blr