you can only pick one

5'4 150 IQ

or

6'5 90 IQ

that says nothing about the quality of life I would live though

5'4 150 IQ

I certainly wouldn't want some freakishly tall gf, so the first one.

6'5 90 IQ

1'2345 iq

I can't parse that!

0.426 inches per IQ point 5'4
0.85 inches per IQ point for 6'5
Seems the 11 inches or +14% height drop IQ/inch ratio by roughly x2 and assuming the inverse is true:
4'5 height would have 0.213 inches per IQ point or 248.8 IQ
3'6 height would have 0.1065 inches per IQ point or 394.3 IQ
2'7 height would have 0.05325 inches per IQ point or 582.1 IQ
2'2 height would have approx(avg) 0.0399375 inches per IQ point or 651.0 IQ
1'8 height would have 0.026625 inches per IQ point or 751.1 IQ
1'2 @ >>6 height would have approx(avg) 0.2-0.01996875 inches per IQ point or 701.0
9 inch height would have 0.0133125 inches per IQ point or 676.0 IQ