Routing speaker wires.

[R TOY]

Hi folks, Trying to feed speaker wires to the rear p shelf/bulkhead. I've got to the panel where the seat belt is housed, which i've removed(passenger side) and threaded the wires up over the rear wheelarch(behind origional speaker) I cant seem to get the wires thro to the top of the petrol tank. It looks like some wires already routed that way but cant find a way thro. Does any kind person know if this is possible or if im ripping my hands to bits for nothing. I'd rather not remove the rear carpeting if i can get around it. Thanks in advance. Dave.