I have had the SLS in 4½ and 5½ m2 for a while now, loving these.
Superlight (Platinum boom), really stable when in your hand surfing, LE seems strong and sturdy, pumps up really fast and nothing can twist not even the pump nozzle as close to the boom attachment (clever), you can grab the front of the bar even faster than the Echo as it sits quite far forward, wide handle make surfing even with a cam in balance or allow for hand switching, really stiff.
Only small thing I have noticed, is when the wind picks up, the 5.5 can have a little flutter sound in the canopy because it is so light, dissapears when sheeted in more.
Was afraid I would miss the longer boom but the SLS is so balanced and you can hold with one hand in the middle but also with two hands very wide without reaching the ends
The best thing about the Slick SLS is it looks great, compared to the square Slick I dont like....
Peter