Your Over Kill just might get you into trouble with air intrusion.
The return line ID has to be almost exactly the correct size (1/4" ID or 3/16" ID depending on which size cap is being used), the OD may vary in size when the hose is not purchased as a return line kit. There are three sizes of SPRING clamps (also known as constant tension clamps) for return line hose, Green, Red and Blue.
When the hose is pushed onto the cap (the cap has a small knob on the end) the hose should fit tight over that, actually making a small bump at that point, using a lube there is permissible, then the clamp (Spring Clamp) should be between the knob and the end of the hose. That is why the spring clamp is made narrow and fully encircles the hose, there is relatively no pressure in the return line hose (1 to 3 PSI). But if a clamp other than a spring clamp is used and doesn't fully encircle the hose, it will distort the hose and possibly introduce air intrusion. Atmospheric pressure @ 14.7 PSI can let air in where fluid pressure is Zero.
Remember, air is a lot thinner than diesel fluid.