How is the flex for the burton Costom on a scale of 1 to 10 with 1 being very flexible?

Tech Specs:

Lengths:

144cm, 148cm, 151cm, 154cm, 156cm, 158cm, 162cm, 166cm 

Shape:

Directional twin 

Effective Edge:

[156cm] 1202mm 

Waist Width:

[156cm] 247mm 

Sidecut Radius:

[156cm] 7.87m 

Stance Width:

[156cm] 53cm (20.9in) 

Stance Setback:

1cm 

Core Material:

Super Fly II (wood with negative core profile) 

Base:

Sintered Vision WFO 

Rider Weight:

[144cm] 80-130lb (36-68kg); [156cm] 120-175lb (55-80kg); [166cm] 165-210+lb (70-95+kg) 

Recommended Use:

Freestyle snowboarding 

Manufacturer Warranty:

1 Year 

Country of Origin:

United States