Reducing checkpoint times on cooked db

We are running Online 7.2 and encountering 45 second checkpoints when the db files are cooked. When using raw files the checkpoints go down to 5 seconds. We are heavily doing insert/delete ops (100 per second) on 2 tables. Changing the LRU_MIN and LRU_MAX to very low values helps a little (down to 40 secs) but our disk is smoking and the overall ops per second suffer because of the additional disk writing. We have tried running with buffered db as well as unlogged db but can not get the checkpoint times down. We are running on Solaris 2.5, 2.6 and 2.7. Has anyone found a way to get KIO type performance on cooked files? Thanks. -Bart