sheet tension

hi guys,
so i though i would give you a little update before again asking you a few questions. first off i have been sailing twice a week on average since i got my 18 and i am loving every minute of it. i am so glad i decided to buy the 18 and not the 16 because it is waaaay more stable and faster, basically a win win. i have been doing some open ocean sailing (very scary with some 6ft waves here and there) and i have pitch-poled twice, once downwind and once upwind.
anyway, my question is about how tight i should be pulling my lines especially my jib and Cunningham (downhaul). it seems that when i pull my jib in completely tight i lose a lot of shape and i even get a small amount of luff in the bottom portion of the sail. is this normal? should i be letting it out slightly to get a more rounded sail shape? my main also has a strange amount of luff in the bottom of the sail (very small amount: almost like a tight rubber band bouncing back and forth). should i have my downhaul looser and should i change it dependent on conditions?
again, thanks everyone for your help and advice. your responses always help, happy sailing,
justin

??? You need to adjust your sheets depending on your point of sail and the windstrength. You should have at least two sets of tell-tails (fabric streamers) on both the main and jib. Adjust your sails so that the tell-tails stream aft (especially the ones on the leeward side of your sails). It sounds like you're just pulling in your jib all the way and leaving it there which is NOT what you want to do.

As for cunningham (downhaul), the windier it gets, the tighter you pull it (in general).

sm

Are you adjusting the jib blocks? They should be back going to weather and forward downwind. That might be your issue. Also try adjusting the hole you use on the jib clew. Mine has 5 holes. If I go up it tightens the leech more when I sheet in, if I go down it tightens the foot of the sail more. Most 18s seem to like the center hole or 1 up in my experience.

Your sails could be shot, too. How old and used/abused are they?