You want the tack and clew patches of say about 12-18" to be clear as they are unlikely to fit in and may jam. You should also allow about a foot because the head
of the spinnaker attachs at a point down from the top of the chute. I gather most do .5 -1m shorter than the luff length. Imho 1m is too much particularly if no account is taken of the head
With an AS the same applies but you measure along the leech because the clew is higher.
If it is a bit long you can pull up a bit out or not pull the sock fully down. If it is short you can have a fair bit of sail flapping about which could be a pain if it is a bit windy and choppy.