The Twin Seat looks mad, if only they made it for the NC35....

i got around the fuel tap probolem by removing the standard one and fitting a piece of thick rubber tube that can be bent around the seat unit so you can still access the tap and switch it to reserve without having to get off the bike, just secure it with a jubalie clip, and mark the positions on the end, ill try to get a picture up, i know it sounds a bit like a bodge but it works a treat and is esspecialy handy if your prone to running out of petrol on the move and need to switch to reserve to keep her running, like i allways do. hope this is of some use, im sure someone will come up with an off set tap or somthing but in the mean time, give it a go.