I'm in the 100% plastics group with a spring bobber and many of the presentations are much smaller than a live minnow can be. Line or bobber twitches and the hook is set, it's in their mouth. In my minnow days we did let them run a bit, wasn't sure where the hook was so we waited. If it isn't inhaled possibly only the head or tail is in the mouth, set the hook and you missed. Smaller plastics are more of a munchie than a meal and is "USUALLY" inhaled. Not saying smaller is the only answer, if they're on a major feed I'm not sure you can put anything to big down there. But if the bite is light or slow, and they are there, try small