I think people put too much emphasis on the lengths of boards. Look at a ruler, see how long 3 cm is? Barely over an inch. On a board that is almost as tall as you are, an inch isn't really going to make that much of a difference in my opinion. The lengths of boards are usually given from the very tip of the nose to the very tip of the tail in a straight line. Some boards might have a big nose and tail that curve way up while other boards might have small nose and tail that aren't very long.

Right on. Effective edge is what matters, but I would also say that weight plays into it, too. You can buy a shorter board that weighs more than a longer one of a design/brand. This has some bearing on how easily you can push the board around into/through turns, a stage that Tony is at right now (just starting to transition from edge to edge, pre-carving stage). I bought my wife a short, light board and it improved her riding because it was easy for her to "manhandle". When she begins to learn to carve more and use edge pressure and body position to turn the board, then I will buy her one that she can advance on.