I'm not sure I understand what you are trying to do, especially when mixed, but it ultimately looks like a pretty basic lookup with approximate match option. You want "largest value that is greater than or equal to lookup value" which means using the MATCH() function with the lookup data sorted in descending order.
MATCH() help file: https://support.office.com/en-us/art...9-533f4a37673a
INDEX() help file: https://support.office.com/en-us/art...2-b56b061328bd
1) Enter your lookup and pallete height values in a lookup table:
2) Use MATCH() function to identify row# of the lookup value MATCH(A2,left_column_of_lookup_table,-1)
3) Use INDEX() to return the pallete height INDEX(right_column_of_lookup_table,MATCH(...))
4) Put that inside of your arithmetic expression G2 =0.25*INDEX(...)+0.15 and copy down.
Does that help?
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