Didn't think a 3-6" piece would go through a planer properly...? Am I missing something...?
The risk with short or very thin pieces is that the leading end can tip up slightly and get caught by the planner head and send it upwards. A sled can help but that doesn't mean there is zero risk in doing it. Taped down will also help but the tape can only hold so much. I think skis or sled is probably safest since you can adjust for a very thin bite and the force is sideways on the piece with no tendency to lift it up.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.