MOT_THST_EXPO,0.3
is still quite low, like for very small props or ESCs trying to do some funky thrust linearisation.
Via our normal method (Leonards graphs turned into formulas) I would expect around 0.6 to 0.7 for 15inch props.
Yuri, are you able to check this post and see if lordvon is correct and how it affects to expo
EDIT
I plugged that in and it didnt make a big difference but maybe it is more correct.
I still suspect a higher MOT_THST_EXPO value would be correct, because even though the red and blue lines dont overlay perfectly, I think the slopes match better when using 0.6 even though the graph lines are offset.