Yes, they are out. Check the specs on http://www.quadwindsurfing.com/spec.php
The convertibles have the exact same shape as the normal Quads just an extra fin box so you can run it as a single fin, or tri fin if you like. Possibilities are endless. Single for pure speed and B&J (I think most would still prefer the quad feel though), tri fin with the Quad front fins and a small rear fin for even more drive, tri fin with a bigger center fin for even better sail carrying capabilities.
But I would say that for most, the Quad setup will easily prove to be the best all round option and you do pay with some extra weight by going with the convertible option.