I've been having bad light control problems with my 13mm Hyperion eyepiece in my 13". Whenever there is anything even slightly bright opposite the focuser--even if it's just skyglow at a pretty dark site--it was flooding the field of view. So I made a simple focuser baffle. I just cut a cardboard ring with inner diameter just over 1.5" and outer diameter 2.2". The inner diameter was arrived at by ray-tracing. The outer diameter fits the focuser tube. I then just slip it into the inner edge of the focuser tube. Because the focuser tube inside is threaded (or just ringed) it stays in. I also added a wide ring around the outside of the focuser tube, inside the scope's OTA, but I don't think this was what made the difference.
Result: Great! Last night, I was able to observe with the 13mm despite the moon, a family fishing with a light hanging over their stuff, and boats in the water.
I also have a large foam light-shield, which I occasionally used, but the baffle ring seems to render it unnecessary.
I expected the baffle to vignette the field of view of my 30mm Super-View, but I left it in for convenience even when I was using that eyepiece, and the views were fine.