Dpm recoil rod reducer system for walther pdp 4" compact - DPM Walther P99/PPQ M2/Long Slide Mechanical Recoil Reduction System

I gave this product 3 stars because I leave a room for my misunderstanding.
I have a Walther PDP 4" Compact (15 rounds standard mag) and this part (3K0-PP1-RSWLTH-MS-WA-2) is indicated as the one for my pistol. The same indication is on the packaging.
Reality: all springs are very long for 4" model. They should be 1/2 inch or 3/4 inch shorter for 4" barrel model. Or it has to be of "captured" type.
The bottom line is: I was not able to put that thing in place. In addition: after some time I spent trying to install that Recoil Reducer System I was thinking: even if I would be able to install it how much hassles I will have each time I am doing field disassembly to clean and lubricate my pistol?
So, I was disappointed and returned it.
Currently I am using "SpringCo" recoil reducing system which is "open" type as well but way more manageable from the installation standpoint and work good for me.
Again, I do not want to say any bad words because of I am a beginner and this review reflects my experience that could be of help to others.