Advice needed -- will I regret a shortbed w/ 43' trailer?

Since the 5er "overlaps" your truck by few feet, your overall length will be longer but not by 10 feet. Backing and turns may feel a little different because the pivot point of the hitch is further forward but with a little time driving I'm sure you won't have any problems. If you were going from a 16' bumper pull to a 43' 5er that would be a big difference but a 33' bumper pull is a pretty darn big trailer already.