Our team has been working with Grails (version 2.3.5) for a little under a year now, and the delivery team managing our servers has little to no experience related to applications written in Grails.

We have several Tomcat 7 instances, both in the test and production environments, with a certain amount of webapps. While some of the instances only containing webapps developed in Java (w/ Spring, Hibernate) sometimes get up to something like 20 contexts with no major issue, it seems like anything past 6 Grails applications (applications much similar to their Java counterparts) starts regularly causing the dreaded PermGen space issue.

The PermGen allocated is currently 536Mb, and the delivery team obviously suggests either using a separate instance for the new applications, or increasing the allocated memory; at the same time they are urging us to verify how these few apps are saturating the memory.

Our impression is that this is normal with Grails apps, but not having any senior Grails developer we have no way to confirm it from experience or better knowledge.
Is 536Mb too little allocated space in PermGen for 8 "regular" Grails webapps?

Update:
To specify what I mean by "regular", these are all couples of front-end + back-end for different services, where the front-end has nothing much more than a list of requests, a wizard to go from zero to a completed request, validates data, persists it, calls a webservice to get a protocol number, and in a couple cases calls an external payment gateway.
The back-end is used to manage requests and performs similar operations.

Every app has maybe around 20 entities with respective controllers, services, and views, and on top of that we have a few classes to handle security w/ Spring Security and an external infrastructure.