One of the fastest "slow" Sub Trunks I ever saw was done in a European circus back in the 60s or 70s and shown on American television. The usual business was gone through and the trunk was surrounded by a large curtained cabinet.
Standing on the right side of the trunk the performer pulled the left side of the curtain shut covering one half of the trunk. He then pulled his side of the curtain shut closing the front completely.
Instantly the left side of the curtain was pulled open by his assistant standing there while the magician did went south. She stepped forward giving the audience time to react and then pushed the curtained cabinet back and proceeded with the reveal of him in the trunk.
I cannot remember the name of this performer, but it was, I thought, an exceedingly clever presentation, skillfully creating the illusion of an instantaneous transposition. I've never seen anyone else use this particular approach.
It was quite startling and well-received.