With the CPE2 there is a limit to the amount of liquid the motor will turn in a drum. I believe it is 600 ml. Even that "sounds" a bit like hard work. Don't over load the CPE2 and use it on the fastest setting which from memory is "2".
I process in both BTZS tubes and occasionally my Jobo CPE2+ with the same tank and reels you use. I have no uneven development but I do not pre rinse. The moment the developer has been poured into the tank I shake it very vigorously for at least 5 seconds then put it on the magnetic drive. My tank is not controlled by a lift arm. The shaking is very similar to the initial cocktail shaker action when you begin processing in a BTZS tube and as Sandy has indicated the film is wet almost instantaneously ensuring even development.
One thing - does your reel  have the little black attachments? These apparently help with even development.
I process PMK in my Jobo and BTZS tubes with no problems at all. Just get the developer onto the film as quickly as you can. You will not have problems with staining developers if you get the developer to the film surface in a rapid vigorous manner, actually any developer for that matter. I have used as little as 150 ml in a 2500 series tank with 2 sheets in a 2509n reel with PMK for a normal development time of about 7 minutes. Longer times would be problematic because of oxidation with that small volume of developer. I think maybe I'm fortunate as I get extremely even development, no pre-rinse and minimum developer. Normally 4-6 sheets in 280 ml of non staining developer or 4 sheets in 400 ml of staining developer. Wetting the film quickly and evenly with developer for me is the key. Definitely no pre-rinse.