If you look carefully at the chart you can see the 10x6 is barely out of the suggested range on the low side. IMHO the 10x6 is a little small for the FX. An 11x6 will work better for sport flying unless you live way above sea level and your engine is starving for power. I have a 10x7 on my FX with a tuned pipe and I'm turning 15,300 on a hot humid day, my little aresti will haul butt, but the engine life will be shorter. Just my $.02