My P-07 has 0 stacking, literally none. Think a Shadow 2, but with a stronger mainspring. The force required to pull the trigger does increase across the pull, but it is linear.
It has the pro kit installed by me and I did a ton of polishing, including areas generally not touched during a standard polish job. Most notably, I also polished the firing pin block, the sear, the pins, and the trigger. I spent over an hour on the trigger bar. The parts that meet the trigger and slide are like glass. Both sides of the trigger are polished to a mirror finish, as is the firing pin block. Not just where the lever presses it, but also where it enters the slide. I also bent the trigger bar spring to reduce the tension, and further bent the tip down so it does not touch the bar.
Lubrication is also very important. The firing pin block hole in the slide has been polished with moly powder, pin channel too. Most of the surfaces that touch things are lubricated with a teflon grease, but I used a teflon oil on all the springs, including the mainspring which is often forgotten, as well as where the trigger meets the bar. Where the trigger bar spring goes into the groove I use moly grease.
My wife has an unmodified P-07 from the same batch, the difference is quite apparent. I believe, judging by where the stacking occurs, that it probably stacks when the firing pin block lever starts moving upward against the block. That means it is either in the block or the lever. Since the CGW lever is a low friction precision machined part, it is probably the block. I did need to do a lot of work on it, so that makes sense.
I would suggest removing the block and mirror polishing the sides. I used 1500 grit on that followed with a 2000 finish. The sear got 2500 and nothing else.