I will have to post my credentials as having never actually fished for flatheads, but I have caught them numerous times while fishing other species….. particularly sauger….
anyway….. on the croix, get yourself one of the hot spots maps… or anything that shows the holes… they are sitting in those holes… most are tough to reach from the shore, but it will tell you if its possible…. if you want just send me a private message and I will try to detail them…. anyway this will work from stillwater UP…… from stillwater down, I have caught them, at the kings power plant intake and outlet (theres a deep hole on the intake)…… then in the hole by the swing bridge in hudson, then theres a heck of a hole just down from beanies on the Mn side below the 94 bridge, then I hear theres some around the catfish bar (go figure!)…. after that your on your own….. Ive caught them out of the miss in pool 2 and pool 4, In pool 2 I would check in and around the deep holes just up from the 494 bridge…… particularly the scour holes behind the wing dams on the west side……
on pool 4, check that deep hole where the vermillion flows in, then there is another spot I have caught them in the winter/early spring on the wisconsin side about halfway to the dam… tough to explain exactly….. but some really big boulders in the area and on the shore…..
thats pretty much all my feeble knowlege holds…