i had luck one year a few seasons back in mid winter with powerbait off the bottom w/ sliding sinker. Used the wind to blow me around in a wind-drop / plunking type of method - it worked for me that day - Landed 2 fish over 12" w/ biggest @ 16". It was mid Feb -but i know if like you say the big ones were down deep - get out the bait and cut the motor -send that bait down deep. I would imagine a crawler and M-mallow combo would bang them up right now !