I like the ability of the MTH engines to be able to drop cars anywhere on the layout. I think that's what is one of the biggest features in O gauge. When upgrading other brands of engines to run on my layout, I still wanted that ability in any engine I chose to run and in any position in a consist. Adding the MTH couplers to USA trains engines was fairly easy. I believe I just screwed them onto the screw mount stand on those engines, using their spring mechanisms to keep the couplers straight. Mounting them on the Aristo, there is just a bit more to it.
First, the coupler post gets cut flush so that it protrudes about 3cm from the bottom of the frame. I then modified some coupler mounts I had from a MTH car. They get cut in a plus design flush to the hole so they'll sit flat on the Aristo posts with the posts stiffners locking into them. The bottoms of these pieces gets a notch so that they will fit around the rear pilot piece as they're screw mounts won't work. Hopefully the pictures will help clear up the descriptions.
The MTH electro-coupler doesn't get touched this way and their return springs will keep them straight.
One other thing that needs cutting is the pilot above the coupler so that there's clearance for the taller electro-coupler. After mounting, I used hot melt glue to help reinforce the assembly. Make sure not to bond to the coupler itself.
This is my first blog, so bare with me.