We are planning on clustering our Groupwise server. Does anyone have any suggestions or best practices?

This is my environment currently:
PE 6650
Netware 6.5 SP3
Groupwise 6.5 SP5
Broadcom nics
4 Post offices (about 220 users on each)
1 Webaccess

New environment:
Netware 6.5 SP3
Groupwise 6.5 SP5
Cluster services
2 PE 6850's
Broadcom nics

What would be the best way to migrate a current GW system to the SAN?
How many post office on each server?
Would it be better to run Webaccess on a different server?
Does GWIA & MTA have to be on the same server?
Will this speed up client access to the application and faster browsing from folder to folder, replying to e-mail, composing new mail, etc...if I broke up the post offices?

Any suggestions or documents would be great..