Keeping all other adjustments equal, by how much does the flex index change when you swap from the B tongue to the C tongue?

Tech Specs:

Shell Material:

[shell] 62 durometer polyurethane 

Number of Buckles:

3 

Micro-Adjustable:

yes 

Flex Index:

100-140 

Liner:

Intuition Gold I.D. 

Thermo-moldable:

yes 

Last Width:

98mm 

Binding Compatibility:

Alpine ISO DIN 

Recommended Use:

Aggressive freeride, race 

Manufacturer Warranty:

1 year