Reverse,
A quick Google shows that you are correct wrt the definition of chordline. It then makes split-flaps a little complex in that, when deployed, the wing now effectivley has two trailing edges, and therefore two chord-lines!
As too your second point, that is basically what I said. An increase in incidence (which is basically what deploying a flap does) leads to an increase in A of A For a given attitude.
mavis- You fink correctley- we're just working out WHY cl changes.
Lowdown- to dicuss whether the pressure differential between upper and lower surface or the reaction to down-wash is the major contributor to lift is a bit like chicken V egg- one automatically leads to the other. I don't dis-agree, but hope I have elaborated!!