I have made many cases also. I never liked the screw on caps. I feel they are too bulky, but checking them for a flight can be unpleasant. I had a cap come off and my 2wt was flopping around half way out on the baggage roundabout. I now use duct tape to travel.
I also use the foam craft sheets to pad the inside ends of the caps. I drill a hole a couple of inches down the tube and the center of the cap to accomodate some knotted nylon twine to keep the two from being separated too far. The twine holes will also allow some venting if moisture is on the rod.