Great reference video. Cutbacks are one of those tricks you never stop improving.., or else you're probably not doing them too smooth.
Doing a nice shallow turn as a set-up is important for gathering enough speed, but I've found personally that "leaning into the rail for longer" is the main thing that helps regardless of how far up or back your backfoot is... However, what isn't mentioned is that when you're cutting back from your frontside, the way you lean into that heelside rail requires more delicate footwork than other surfing maneuvers.
A lot of people lift their toes up on their front foot to lean into their heel, but I've had more success by folding my foot over slightly to apply more controlled pressure into the rail. Almost like your pressing into someone's face with the back of your hand. Also, if I feel like I'm not transferring the weight fast enough, I pull up on the rail manually and whip into the cut. Works like a charm for a regular cutty, but throws you off a bit if you're trying to finish off with a roundhouse foam climb.