The tweeter was mounted in the same place as the OEM, using the same bracket. The original was unscrewed and the glue bond broken. I bent the little tab back and used steel high-strength (unnecessary) epoxy to mount the JL tweeter to the bracket, centering it slightly forward of where the other was, and set it asside to cure.
The woofer was more challenging. The OEM Subaru mount uses a larger diameter 3-hole mount. Most normal speakers use something else. Also, the JLs are too deep to be mounted directly to the door sheet metal. Mounts had to be made. I couldn't get a good reference measurement of the clearance behind the inner door panel, so I just went ahead with a guess. My choice of MDF (medium density fiber board) is either 1/2" or 3/4", so I made two 1/2" mounts and stacked them to equal 1". The speaker cleared well. However, after I got it all together the inner panel had a way to go to fit well. So, I went to a single 3/4" mount. I counter-sunk screw holes for the mount mounting screws. Self-tapping sheet metal screws of the right size thread right into the OEM holes. The four speaker screws were wood screws supplied by JL Audio and screwed right into pilot holes drilled in the MDF. I used silicone caulk to seal the perimeter between the mount and door and between the mount and speaker.
Clearance of the inner panel was fine after a little trimming, BUT a window stop was now set for collision. With a dremel and a cut-off wheel, I trimmed about half of the protrusion of that screw and white plastic thing seen in the picture. It is important to take it slow to not melt the plastic.
The speaker box states "2.81 in. mounting depth". I never measured it, but I had to remove the 3/16" thick rubber cover over the magnet to buy more room.