I've had a fair amount of success using medium fat head minnows within the top 5' - 15' of water just under the ice. Single size 8 or so hook (I use circles but realize they're not everybody's cup of tea) and split shot 6" up (keep it tight so the minnow fights the shot) with 4' leader of 6# - 8# test. I tend to set my tip-ups on top of the best depth break in the area I'm fishing but have caught them out in the middle of flats and over deep water as well and feel location is more luck than science when all is said and done.
