iBGP Scaling

Hi List, We are looking to move our non infrastructure routes into iBGP to help with our IGP scalability (OSPF). We already run full BGP tables on our core where we connect to multiple upstream and downstream customers. Most of our aggregation and edge routers cannot hold full tables and it's certainly not possible to upgrade them. Is there any reason why we shouldn't filter iBGP routes between our core and aggregation layers (we plan to use route reflectors) or should we be look at using a private AS number per POP? Thanks Dave