As long as you can keep a good taught mainsail, the main sheet will bend the mast backwards and so keep the luff of the jib more or less straight. But when you slacken the mainsheet in a blow, the jib will slacken its luff as well?
Thats the theory and thats what I´ve seen when I´ve been to France watching old boats. But maybe its coincidence and maybe I´m wrong. I would like to try a boat with a lug sloop one day. So next time I go to France I hope someone will invite me to test one.

As I wrote before, the Aber looks VERY good as a lug sloop. But I have a question: The overlap of the lug is very short. Does this mean that you need to fit it with a kicking strap in order to control the twist of the sail. Being an ex racer, I dont like sailing with a rig where I cant control twisting.