The ORR rule for sheeting headsails applies. ( 10.05 ).The staysail clew can not be further aft of the LP line of the largest jib. If the tack is moved towards the mast as in Blur , the LP of the staysail would have to be shortened to about 65% of the "J" measurement . Not sure if the smaller sail would be any better than a larger staysail tacked further forward. Say 85% of "J .