I've run machines both ways, with and without a cotter. I ran on 2 1811's and a 1050 without one and never had a problem. That being said, I'm using washers and cotter pins on the 1864 its on now to help "lock it in", side to side wise. It seems like using cotter pins and washers helps to take up the slack and stop potential frame twisting, if you happen to hit something sideways. That's how I see it, at least.
