Marine on St Croix Catfishing?

Hi guys, new to this forum but I will be probably be forever known as the dude that caught the giant sheephead! I have a 14′ x 48″ wide johnboat that can go most anywhere and I fish mainly from Marine down to the high bridge. I have a fascination with cat fishing, but know every little. I managed to catch a few channels on cut bait, but I really want to catch a flathead. What’s the fishing like for cats up by Marine? I know of plenty of deep holes, but does the current matter or is slower water better? I think I can get some bullheads from the local ponds by me so I just need to find time and convince someone to go.