I haven't seen this done on a J30 but I would be interested too. An asymmetrical chute in a sock makes alot of sense for shorthanded sailing. The problem I see is that the fore-triangle on the J30 is so small that an asymmetrical spinnaker might not be very efficient. It might spend most of its time hidden behind the main. I'd consider adding a spinnaker halyard at the masthead to get a bigger chute. If you're really gung-ho, you could retrofit a bowsprit like the newer J/Boats. If somebody came up with a kit for that, I'd definitely be interested.