"Lightproofedness" of plastic cassettes for bulk loading
I have a number of plastic cassettes for bulk loading, the kind with the twist top. I haven't yet loaded any of them because I am wondering how light proof they are. Here's an image (and I know it doesn't show a plastic cassette but it gives an idea of my concern, I hope):
The left-most part of the spindle will simply just "lie" against the bottom of the cassette. And it doesn't even seem to fit well in the cassettes hole either, it's possible to wiggle it back and forth a bit. I know the spindle has a pretty wide "brim" but is this really lightproof enough? If not, must I load the cassettes in a dark(ish) room to reduce leaks?
Cheers and thanks for any insight.