Hi Jonathan and Mark
Although the lug sail is similar to a junk sail when seen in profile, it takes quite different measures to achieve camber in the junk sail’s panels. Have a look at this month’s BOTM, Malena. There you can see the lots of bagginess, which was needed to achieve a camber/chord ratio of 8%. In Newsletter/Magazine 30, p.21 you can read how I did to achieve that bagginess.
Cheers, Arne
PS: You can of course also make the junk sail flat, and in that case things get simpler - at the cost of some performance.