Plenty of info on here about XS-Ribs:
You can get have a backrest made up for those sitting in front on a double jockey as well. Myself and Pettal enquired about this and Barnet said they can have anything made up as long as you provide a sketch of how you want it made.
As for who laminates XS-Ribs, they are a major UK manufacturer with a huge production facility and so can turn out the hulls quicker than Barnet can fit them out. As a result Barnet are moving to a larger premises this Christmas so they can keep up. Looking at the hull I would say it is very similar to a Phantom, but I don't know who laminates these or what facilities they have. (Rogue, do you know??)
Is it possible that XS could be using Tornado hulls and having them moulded by a different manufacturer, after all Laurence Lock is a MD of Tornado.
Anyway regardless of who makes them. They are very solid, well built boats with good rough weather ability and sharp handling and performance. They will be a lot cheaper than Ribcrafts also.
I own an XS but would be just as happy owning a Ribcraft too as they are boat equally as good.