I don't think the S5 plates promote Side to Side flex. By looking at the photos, i think it allows set distance between plates for width of board. Difference between uni-platform vs 2 platform is to reduce weight of the plates, not to promote/allow side to side flex, I think. Some of reviews has been posted in some korean forum and it was softer than other plate system.
Anyway, here are some translation of the product page.
Material: 7000 Duralumin, Heat treated and tempered on 45C Steel Axis, Stainless Brackets.
Difference: Very rigid on torsional stress. Plate+Bindings combo enable (F2 or S5 bindings)
Spec: Weight 2.1 kg. (With binding bails: 2.7 kg)
- Lifts/Cants can be applied
- Custom (Regular/Goofy, Stance Width), Binding Angle is 50-55 Fixed.
Noticeable Ride Difference:
- Very easy to turn (GS feels SL)
- Buttery turn Initiation & exit
- Plate+Binding Combo height is about same as just bindings alone.. No weird feel from height.
In the reviews, I noticed that he used softer setup (Oxygen proton GS 178 / SL 160, S5 Isolation Plate, Deeluxe Leman). That reminds me lowrider's comments on softer setup for softer boards and harder setup for harder boards.