I tried the vision 2 style carbon props on my FC40 and did not like them all that much, I had to really mess with the gains to even get it to fly right with out it trying to crash when descending it would start wobbling from side to side and would start oscillate so bad it was hard to control and would just start dropping out of the sky and almost bit the dust a few times. till I got the gains right. and then I dint get any real benefit out of them. It even dropped my flight time down some. THo it could climb really fast and seemed to be more responsive on turns and breaking. for some reason they also would let me fly a tiny bit faster when in GPS mode then the stock ones would, On the other other hand when in atti mode it shaved about 10-mph of my speed. Which was strange considering it usually boogies when in atti mode with the stock ones. So I just switched back to the old ones this past week ends and my speed went back up. Even gained a new personal speed record on flytrax and hit 59.93 miles per hour as soon as i went back to the stock props. Woot woot..... Even in a good wind with the vision style props I was in the low to mid 40's speed area.