That works. There is a Youtube video somewhere of a guy doing a speed test with OA on vs OA off (non sport mode) and he got approximately the numbers I quoted. I did a similar test and got similar results.
I tried it today. There is indeed a significant speed difference with OA off. Nice to keep discovering new things about the drone.
I think I will keep mine on for now though, I can just fly in sport mode if I need more speed and if I get into trouble quickly switch OA on by going back to normal mode. I prefer the quick hardware button instead of having to navigate through menus.