A more aerodynamic sail on the Speed Series, leading edge shape & a pronounced (larger diameter) curve built-in (They will dead-launch!), no venting, shorter overall height, the shockwave will do everything 50% faster,. . . . . 60 or 70 mph forward and half of that in reverse. Even a quicker side-slide. The secret is still control though and that means "owning thy hover".
I've owned all of the speed series kites (except that 4-8 traction monster). The only one I kept is the Supersonic, it doesn't get to ride in my A-bag either. It's the smallest and fastest of the bunch. It's almost impossible to catch (3D flying), as the speed series captures the up-wind and rights itself in a big graceful horseshoe-shaped arc, heading back away from the direction you yanked it into. Throwing the supersonic is like pitching a javelin though, it cuts thru the wind just as a laser would pass by air undisturbed!
I've run a trick-line around the parameter of the sail (thru the end-caps) so it will flick-flak instantly and not snag a flying line. Looking at the back of the sail, you'll notice a bunch of knots and washers. Those need to be snag-proof! Cover 'em with electrical tape for a quick fix. more permanent is little covers placed over them (3M's 9460 bonding tape & belt-loop width of nylon, poly or dacron, ~no sewing!~ make a perfectly fitting paper template first).
With the trick line installed the supersonic will "drill for oil" (flick-flak rapidly, balancing on the ground, on it's leading edge) which is a cool trick most spectators have never seen.
I'm on a Zen kick right now, because it's summertime in the District of Columbia/mid-altlantic states. Five months out of the year we have zero wind, no point in carrying a speed series kite or the higher wind fully vented stuff.