Looser than the Disco? Well... I think what you are looking for is increased responsiveness. A couple of things can do that for you, but they all come with a price.
Go thinner in the rail. Small wave boards usually have slightly more volume in the rail, and the Disco has thicker rails, which let you push off them in slow, weak surf, and add float. Thinning the rail, and crowning the deck, will ball up volume through the middle of the board and let you sink the less buoyant rail more easily. You won't get the float, planing ability and drive a thicker rail provides, because as a thinner rail sinks, it drags, too. But it will feel more responsive.
Use a relieve feature in the tail block. Small wave boards have wider, thicker tails to make the most of the minimal amount of energy small surf provides. Consider a cut-out type tail block rather than squash to make going rail-to-rail easier. A swallow is a good example, which is why a lot of fish type boards with wider tails have swallows, bat tails, crescent tails, etc... The tradeoff is less planing surface and less speed, and somewhat reduced wave-catching ability.
Vee. In small wave boards, vee in the tail, rather than concave all the way out the back, makes going rail to rail easier. But you lose speed and drive, because vee makes the board ride lower in the water, and with more drag, but also more responsiveness.
Fins. Fewer fins, smaller fins, fins clustered closer together, and fins shifted forward, all loosen up a board. But you lose drive. If you have any adjustability in the fins, try moving your trailing fin forward as far as it will go.
i too was intrigued by them as i saw a few guys killing it on them at my local break (moco NJ). i am big fan of alternative shapes (no longer even own a true thruster). from knee to head high they made it look fun, but i had a hard time dropping the loot on something i had never tried. i found a local shaper who was cool enough to let me borrow a 5"5 mini simmons for a few weeks. after that i was sold, got one shaped to my specs and its been my go to board ever since. such a fun board! for the last year or so i have ridden either my mini or log, ha talk about 2 different boards, log is double the length as the mini. but just remember, the mini is not a thruster, so don't expect if to perform like one.