Warning, this started out of shear boredom and the fact I own too many Matrix markers. This might not be for everybody, but its just good info on compatibility between markers IMO.
First this started out as a curiousity as to what bolt kits work in which markers. A PM8 bolt kit less the front can was used and was tested to work. Next a DM9 bolt kit same as before required only the swapping of the front can for the stock PM7 can. Below you'll find pictures of the bolt kits next to each other to show the same dimensions in length. Only the bolt diameters and the corresponding counterparts were the changes made to.
From Left to Right PM7 Bolt, DM9 Bolt, Bwing bolt w/ PM8 back cap
Front Left PM7 front can, DM9 bolt can
From Top to bottom PM7 bolt, DM9 Bolt, Bwing bolt w/ PM8 back cap
Right top PM7 front bolt can, DM9 bolt can
New assembly consisting of PM7 front can, Bwing top hat, Bwing bolt and PM8 back cap
Assembly installed in PM7
The test marker functions a lot smoother. It was noted that the DM9 stock internals were less poppier sounding as that I believe is contributed by the air flow restriction of the soft bolt tip on the Bwing assembly. Marker was tested with DM9 internals in games. Bwing installation only test fired, but forsee no issues to arise. It was also noted that the PM8 backcap didn't seem to thread right into a stock DM9 top hat.
Next possible future compatibility test will be on a friend's PM5. Bolt kits looked similar in length in side by side comparison.