I've put buttons on many bellcranks. But I've never built a whole engine. In an event that allows unlimited engine work, button leadouts are no big deal.
All events had displacement limits until they started allowing electric motors in stunt and scale. As far as I can see, we still have displacement limits in speed, racing, combat and carrier. I've never seen an engine measured. I know they measure engines that set speed records, I just never witnessed it myself.
I guess I somebody's conscience will allow him to win The Brodak with an oversize engine he can take it up with Saint Peter.