I was wondering what makes a lightwind board suitable to plane early AND to go upwind. I have had the loose AX 150 as my lightwind board for years and this board planes quite early. The board has a big rocker, but this does not really affect the speed I can reach. In very light wind (around 10 knots), although the board still planes, it gets hard to stay upwind, even with my Flysurfer Speed 17. I have read reviews about SS glide and FS Flydoor where it should be possible to stay upwind below 10 knots. So what determines their superiority in low winds? Is it the lack of resistence? Do they just float better? (My AX doesn't sink that easily either...).
Bottom-line: would I benefit from buying such a board?

The Glide and Flydoor are both almost completely flat - it definitely helps with accelleration and "gliding" through the lulls.