Tip stall will happen on those at even higher speeds if your elevons have to much angle to them as well. I maiden a xpd8 I had built, let a more experienced pilot take it up after he gave me the nod on how it flew I took it made a couple of passes felt comfortable and went to climb up and do some spins and loops after giving full throttle for the climb from straight and level I went full up. the flaps were set to high it wiped all my lift and lawn darted from 100'