So far from all the long rangers around here you will have to fly 30 mph (28 to 31) to get max distance for battery life so s mode it is, if there is little to no wind atti may conserve some power but you may be all over the sky. Try s mode at 30 mph for your first attempt. IMO
I used to do my long distance runs in P mode months back, but at or around 18 mph, I wasn't getting the speed which the long distancers are using to get their super long flights. My flights in P mode were out to over 16,000', and I even did one tonight at 17,090'-a flight I wasn't able to do in Tap2Fly due to it being dark.
So, to get a little better speed, just as I said above, I began using Tap2Fly since I'm getting 22 mph with it. I also like it because it is essentially "cruise control" for your bird. My longest distance with Tap2Fly is 19,736', but it still isn't competitive at that slower speed, so I will eventually find a way to maintain an optimum speed while using Sport mode. I will probably place a small sponge in front of the right controller to stop it as around 28/29 mph so I won't have to concentrate on maintaining that speed.