Sizing for OAAM 11g

We are trying to procure hardware to begin an implementation of OAAM 11g.  Our initial goals for OAAM are: (1) user interface for password changes (max of 1000 changes per day), (2) to begin device fingerprinting for core business apps, and (3) to allow users to self-select advanced authentication methods . 

We are wondering if we can install the OAAM application on the OIM servers as in the HA documentation.  We have have two app. servers and a two node RAC cluster for the database.

We are also trying to figure out how much additional disk storage we might need to plan for "online".  We are looking at the option to move the analysis data offline to a reporting database for OAAM.