Twin engine does not need dual exhaust. Looks cool though.
The concept has proven to cook many a nut sack. Its awesome for aesthetics but after an hour of riding in 103 degree weather it loses its appeal. All the metal in the frame of the bike heats up including the seat. Its sweaty crotch all afternoon. I don't like how the components under the seat get super heated. I also do not like the problem that is posed with license plate mounting as it always looks poor mounting plates and signals around underseat exhaust.
Maybe with R3 it would not be as bad as 4 cylinder bikes I have tried. Doubt it though, exhaust pipe gets plenty hot.
The guys that ride under seat exhaust are always willing to trade bikes