Why connect the new filter between the stock filter and the CP3 anyway? What benefit will that give? Better to mount the new filter before the stock filter. That way the stock filter can catch any debris that gets into the system from the new filter install. Stepped filtration you say? That is misunderstood by the interweb experts. The main reason to go with stepped or staged filtration would be if the dirt load of large particles is so high that a finer filter would prematurely clog with the large particles making the change intervals unacceptably short. Judging from the change intervals reported on this forum, premature clogging due to large particulate is a non issue. So it is better to run two 2 mic filters in series than to run a 10 mic and a 2 mic filter.
Add a good water separator and then the fine filter before the stock housing and call it good. Throw the finest filter you can get in the stock housing if it makes you feel better. And do yourself a favor and do not mount the spin on filters to the engine. It amazes me that guys go nuts to buy the filter with the "very best" specs (like that filter is somehow light years better than the other similar filters :rolleyes) and then they go and degrade its performance by mounting it to the vibrating engine. D'oh!