I just want to add, i have caught plenty of carp in the current, don't be afraid to fish in current, especially if you are using 3 ounce sinkers!
Also, bolt rigs work well near rocks and structure but on a muddy bottom with few snags like the charles, forget the bolt rig and heavy sinkers in favor of lighter weights and treble hooks i never use anymore, one too many horrible hook ups and cats can find a way to get hooked with all 3 hooks, what a mess.
Three tonight - 7, 10 and 13 lbs. This was my first time catching when using method balls, and my fish caught on corn. And the one that got away would have been a personal best.
My first fish of the night was definitely bigger than 13 lbs. It ran to the other side of the river - about 80-90 yards, and then the line went slack. I thought it had broken off the line, and started reeling in the slack. Halfway back, I suddenly felt the sinker again. I think it had doubled back towards me, and shook off the hook. Based on the run, I'd estimate 15-20 lbs. There's plenty of water between Newton and Needham dams for carp to feed and grow.