quad fins havent been out on the market but they have been experimented with, they found to be similar to twinsters but had way to many problems, becuase the angles had to be just right and cavitation was to much, couldnt get nice turns, etc so they gave up.
but thrusters are also getting back into the market, robby naish was the person who really got them populare, but then they died down, but now they are comming back again, and they are ment to have real advantages over twinsters, some points given in windsurf magazine why is "it combines the bes of both worlds" and "the center fin adds contol in the same way a single does but you get even better maneurability than cn be achived with twinsters" "the center fin alowd teh side fins to be placed further apart so they dont interfear with each other, so if one side fin looses grip in an especially hard turn, you only lose between 20-33% of the control (depending on the toTAL fin area)" and than the final dot points of the advantages are
- ealier planing
- improved up wind drive
- a shorter turning radius
- more waves and more turns on waves
- easier turns
- mre control over the top turn
- sailing in shalower water
- the board does not rail ride when extreemly over powers
- reduced fin out
sothats waht the"windsurf" magazine has to say about the advantages of the tri fin over the twin fin,
sory about spelling not very good at typing and reading at the same time