The number of members could be impacted by some factors, such as whether or not the GM is running protocol services (it generally should not be, and this is more important the larger the Grid is). For a 2225 that is a dedicated GM (i.e., it isn't running other services), the member count should not exceed 100.
Re: What is the limit of members within a single grid?
With that said, I would highly recommend you consult with your Solutions Architect (SA) when it comes to sizing questions specific to your environment.
