I don't use twisted stock, cupped stock I plane cup down first. But I'm talking very slight cupping. If it's really cupped, that's a bad piece of wood I don't want to use. It's really advantageous to have a wood pile to choose my straightest pieces for my nicest projects. I try to get quartesawn wood which stays stable. If you have twisted stock, that twist is embedded in that piece, if you get it flat, it still will want to twist as time goes, and that goes for cupping as well. Plane a twisted board straight, make a cabinet door frame and the door may not stay flat and warp. Milling thousands of board feet has taught me that twisted boards are the junk boards. So if you use twisted wood, you may want to try other methods, as I'm not sure what woodworkers do with twisted wood. I avoid twisted material all together. If I buy stock at the lumber yard, I'm buying oversized wood I plane down, and I don't buy wood if it's twisted. Twisted wood is fire wood to me. Cupped wood planes flat no problem.