On these dimensions, you have to be dead nuts on. Also, you need to make sure you get the jamb nuts tight w/o changing the dimensions. Good luck. When you get it exactly right, they work just fine.
Also, when coming out of reverse, I have found that if you let the handle go and let it snap back in place, it never fails to fully return versus following it back into forward with your hand on it.
Sometimes you have to move the sled a bit to slacken the chain, if the chain is adjusted right to spec. I leave the chain a little loose because of this.