i havn't had any issues. i even had smaller boards, 1/2 inch and taped (tape on the sides and not the top were its gonna hit the planer blades.lol) several of them together and ran them through. I'm sure it's not recomended. I thought about building a box for the thinner boards to hold them but, I don't do it enough to worry about it. I do have one saftety tip. if your planer isn't bolted down and your running 2x6x8 rough cut through it, make sure ya support the boards or it'll pull your planer off the table.