By keeping the
jib trimmed until it is luffing you add pressure to the tiller in making the turn thus braking your forward movement. When you decide to tack you should begin to loosen the
jib sheets to facilitate the turn. I agree that you want to maintain some control on the flopping of the clew. Thats why you just don't let it fly out. Begin trimming on the new side ASAP but only at a speed that keeps the
jib in control and does not put undue pressure on the rudder. You want to slightly over steer and simultaneously trim the
jib to its proper trim and THEN begin to steer up and trim to your new proper course. This will help to maintain speed. You need speed to turn and you need to speed to lift.
Jeff