Don't some of the Aussies regularly build XS motors between 810 and 830ccs?
I may have been high but....
Does anyone remember seeing pictures of a "square four" XS that someone made? It used two heads, two cams, two cranks/cases, two sets of barrels. The rear cylinder head was turned around so the intake faced forward and exhaust faced back (obviously, needed a custom cam but not impossible) It used two cranks which were tied together on the generator side and used one clutch. The front pair had the transmission sawed off and joined to the front of the rear case. It used two carbs- the intakes for them stuck out of the side of the bike. Not sure where the iggys were- probably on the ends of the cams.If you have ever seen an Ariel Square Four, you know the concept. 1500ccs with a 750 kit in each set of barrels.