I have had fish hit the 9" ones too. Hooking up is the problem. If you don't mind not being weedless, some kind of treble hook rig will dramatically increase your hookups.
I never had the patience to use the bigger ones much, the smaller Sluggo's seem to work just as well for me.
All that said, I can't see any reason why they won't work under the ice. I haven't tried it, but I will.