I'm a firm believer in Kadee couplers. It looks like the coupler mounts are the same as the scale coupler conversion they were offering in freight cars at one time. Despite their issues they got me started in converting everything to Kadee's. In your case these might be worth a shot and give the Atlas adjustacouplers a try. I would first remove the the stock Atlas centering spring and replace it with a Kadee which is much softer. You can also file back the coupler box to allow more swing. With this setup the couplers will actually stretch out a bit as the cars start to move. With truck mounted couplers and couplers that can move more freely you should be able to adjust the length and get it working reliably. You want have issues with a thumbtack hitting the rails.
If you are going to run this as a consist without doing switching moves you should be fine. A little care needs to be taken when backing up. You will need to leave the stock 3 rail coupler in place on the head end car to mate with the engine.
If you want to try this setup. I can send you some couplers and Kadee springs.
