Planing-gybes on a FW board are certainly possible, but it is purely technique based and very different to the technique used for gybing slalom boards etc ...
There's a more in depth article about it here if you read down a little ...
carbonsugar.com/technique/the-learning-plateau-and-how-to-climb-off-part-ii/But basically, don't keep the sail 'open', you want to tuck it a little at the beginning like you would a slalom board to keep the rail pressure initiated throughout the turn. The rest of the gybe is about shifting your weight and the sails weight at the exact right times to keep the momentum of the board and whilst doing this to 'ooch-pump' the board with your legs (ie, like you pump a surfboard in small sloppy surf to keep on the wave). Read the above article for a better breakdown of each step... the rest is just practice, practice, practice.
Once you've got it, its actually a cool sensation to plane out of a gybe past people in 8 knots... haha.