Mike and Ollie thanks for the help so far.

@Mike,
The sizes are: 180cm span, root 43 cm, tip 26cm

@Ollie
>>In this case the 25% chord line's sweep forward<<
No streight trailing edge, not leading edge. The 25% line sweeps backwards. See planform.
Both sections tip and root will be 8035, but if you have a different suggestion, please mention.
So if I conclude further, that is why it is said that a giles tends to tipstall because these effects add on here.