As many companies F-One usually have 3 sizes by models : small / medium / big.
I'm an average rider (175 pounds) and I have the average size 136x40.5, wich is perfect for 80% of my rides. I have the 2014 TRAX (not carbone) and I love it, but I've tried the carbone model and it really worth the extra 100$.
Last year I got the TX6 136x40, and it's was perfect for freeride but not for freestyle. In 2014 they have introduced the TX6 flat channel on the TRAX making it much more versatile : earlier planning compared to TRAX 2013. That's why I bought it. Regarding the sizes variation, not so sure about matth
's comments. If you look other boards/brands 1 to 1.5cm variation by sizes is common. Just make the math
with other brands/models
Regarding the lightwing version (140x45) I had a chance to try I in two totaly different situations:
First try in 15-20 knots with a 9m kite in choppy conditions. First impression was "this board is smooth in the chop, no splash, I can hold it easily in 20 knots, board is light, I can pop hard and landing are smooth event if the board is big". Logically my conclusion was : it can't be a good lightwing board!
Second time was before leaving a kite trip in Cuba. I was taking my flight that day and didn't want to get all my stock wet. F-One sales rep offered me to ride it's 2015 demos but most them were on the water. Wind was blowing 10-12 knots and people were riding 12-14m kites. The only demos available where a 2105 Bandit 6m and the ligthwind Trax. I was flabbergasted to be able to ride in these contitions with a 6m kite!
If we are an average rider (160-185 pounds) with a big kite (14m), you want to maximise "fun time" on the water, this is your board! Again, the flat channel in the center seems to be working very well for early planning. It's rocker on the edge and it's flex deals with the chop and the landinds. Bigger riders with 17-19m kites will also love this boad.
Big rider (220 pounds) in a sub 8 knots wind quest, will need a bigger board (143x47). But at this size "fun factor" goes down!