For quite some time now I have been looking at different companies doing a wave sail in the 5.5 range that is both light and suits my style of sailing. In the past I have used mainly Neil Pryde Atlas and Alphas. Those sails are great for heavier riders especially in the smaller sizes. In the bigger sizes I always felt they were on the heavy side. Especially on those days when the wind is so light you are not really planing on the way out the extra weight can be a struggle.
Last season I switched to the Neil Pryde Combat HD. I think those sails are a great compromise between power and easier handling.
That said I managed to get hold of a 2014 Severne S1 5.6 and Blade 5.5 as well as a 400 Redline carbon mast to demo.
My impressions of the S1 below are based on 6 sessions sailing in variable conditions of 10 to 25+ knots. I paired the sails with a Severne Carbon boom from last season and a Neil Pryde UTX aluminium extension as well as a Fanatic Quad 101 / 93.
Build quality: The sail is light … I mean really light. I used some luggage scales and in dry condition the sail weighs an impressive 2.9 kgs. about 100grams less than what Severne states. The full rig with the recommended mast and a Severne carbon boom came in at 7.4 kgs. In comparison my 2012 5.8 Atlas weights 4.05 kgs alone. I think they managed to strip weight by making small changes: e.g using 4 instead of 5 battens, using a steel ring for outhaul instead of an elaborate pulley system. Speaking of which. The down haul rollers seem to be made of some sort of none-corrosive type plastic instead of metal. That's a nice detail given the amount of corroded "stainless steel" pulleys I have seen over the years.
Overall the sails seems a good compromise between build quality and saving weight. It doesn't look quite as sturdy as say a Combat HD or the Blade but it's certainly not a cheap looking sail.
The batten tensioning system needs an allen key. Severne provides one with the sail that's stored in the sail bag. I guess that's another part you can loose but it works well.
Design: I won't comment on the design as that comes down to personal taste.
On land: With the recommended mast the sail is super easy to rig. It needs a 400 mast rather than a 430. It slips without resistance into the mast sleeve and attaching the boom is a breeze due to the large cut out. The rigging guide that comes with the sail is easy to understand and if you follow it you should be able to get the most of the sail.
On the water: Did I mention the sail is light? I mean really really light. It's so light in fact that I laid it on top of other similar sized sails after my first session just to check it was actually a 5.6 sail. It feels more like a 5.0 or 4.7.
Most of the power of the sail seems to pull above the boom rather than putting direct force onto the mast based. Combined with the light weight this means the sail makes getting out past the break in none planing conditions really effortless.
The pull above the boom also makes rotational moves like a forward very easy. You seem to get this extra whip to move you through the last part of your rotation.
I can't compare the sail to last seasons in regards to range as I have't used it any S1s before but to me the sail seems to have a pretty good range. Even on the verge of being overpowered I didn't have to fight with the sail. Perhaps it's my weight that resulted in more swing of the mast tip and power release. The bottom end needs a tad more wind then a power wave sail. Probably not as much an issue for lighter sailors. That said it does give you enough lift to get out past the break.
Overall this sail really surprised me. Looking at it rigged on land I expected it to be really twitchy due to the shape and the 4 batten design especially once you are overpowered. But that didn't happen.
Overall Impression: I think I mentioned it already but this sail is really really light! Overall the S1 5.6 is a great wave sail if you are into riding waves and live in a place where you will often spend time in sub-planning conditions trying to get past the break. For heavier riders the reduced weight really helps. Yes, you are giving up some low end power but who cares when dogging around is so effortless. In places like Gerroa this sail would make a lot of sense.
If I'd have to find any faults I'd say the build quality makes me question if the sail would survive heavy reef contact but I guess you can't have it all. Also if you are a heavier sailor looking for a sail to just blast back and forth perhaps look at a
Blade, Combat or Atlas instead.
I'll try and get some photos up separately.NOTE: This is my own personal opinion. I have not been paid for this review nor am I a team rider or get any other incentive... not that I would say no that of course 
Here some photos. The colors are a bit off. I couldn't be bothered doing any color correction.
Batten tension system requires M5 allen key. Severne provides a small tool... looks like it also includes a bottle opener 
Boom marking on sail make it easy to attach the boom at the exact same spot each time.
solid mast protector despite the sail being very light
simple but effective outhaul
sail rigged with recommend mast and mast twisted.
Sail rigged with recommended mast.
Size comparison. NP Combat HD 5.3 vs S1 5.6.
Great review!
any thoughts on quiver spacing, as they have some "odd" sizing
ie for example:
5.6, 5.2, 4.8?
or 5.6, 5.0 and 4.5?
