In the earlier days of this forum I did experiment with using Cal Hypo granules in a Hayward CL-200 feeder. First, the warnings are all true about the risk of explosive problems, and, the statement about various forms of chlorine reacting violently with each other is definitely TRUE. Concentration, pressure, and heat are the undesirable results that lead to disaster. To be safe, never mix the forms of chlorine directly where you can get any or all of the above results. So, to be on the safe side, never mix in any feeder at all.
That all being said, I did try fabricating a kind of time release capsule for granules made of a piece of 2" PVC pipe capped at both ends with a bunch of holes drilled in the pipe. After much fussing (experimentation) with the number of holes and hole size, it did work. Was it worth the effort in my case? NO. I reserve the chlorinator for pucks when I need to raise the CYA, and just dump CH granules in the skimmer and let them dissolve in the sand filter. I have a low calcium hardness reading so I can benefit from the convenience of cal hypo compared to bleach. I do use all three forms of chlorine as appropriate.
Al