Good performance!
The only thing I would say is slow it down. Put some filler in it. You need to make the transposition as different from the vanish as possible. Put the deck in the box, or in the spectator's hands
Also, instead of controlling it to the 4th via overhand shuffle & that awkward top count you did, why not use a 3 card tilt, or a bluff pass. Then there is no need to shuffle the deck, and you can just thumb off the top 5 cards. Or You could even control it to the second using one of the same moves as above, and then count off 5 cards one at a time, thus getting it to the 4th. Either way, you would then flip the cards face up as you do the "biddle move", thus leaving the selection on the bottom. You can then give the deck a cut, and put it in the box, or the spectator's hands (or both), as you put the packet somewhere else (preferably in the spectator's hands, or on the table near the spectator).
I just got an idea for a similar effect, but instead of using a Biddle grip, I would use a Count Cop.