every now and then, vacuuming case interior is a good thing to do
using a rubber reducer from vacuum hose to pvc tube was simple.
the pvc in 1" inch, 1 1/2" inch and 2" inch diameters, all cut same to 36" inch lengths.
be sure to bullnose the pvc tube on the side you're putting into case interior.
make it smooth and it will pay you back plenty.