Morgan O says:

1. What says that the main should be bigger?

Nothing really, but it has been found over many years that you are able to
"change gears" more efficiently this way. Reef main first, then drop a size of
headsail, then reef main again, then remove headsail completely, then reef main
again, then bare-pole in the least dangerous direction ;-) With a really
large jib, your first "gear change" involves removing the largest sail on the
boat.

2.Some boats have M/F-ratios of 4. That seems really stupid.

From someone who obviously has little knowledge of sailplans, why do you use
the word "stupid?" Do you really mean "I don't understand?"

3. Is a self tacking jib a matter of importance when regarding the
M/F-ratio?

Not necessarily

I suggest you find a book called "Sail Power", by Wally Ross, and look into
these things deeper.

Steve
Stephen C. Baker - Yacht Designer
http://members.aol.com/SailDesign/pr...cbweb/home.htm