I believe WE and gpa have a similar impact on the rate of IQ increase.
A good rule of thumb is every .1 gpa equals between 3 and 4 WE points. It varies a bit depending where you are on the scale, but 3.5 WE per gpa tenth is a good starting point.
If you use that ratio; a 3.0 gpa with a 50 WE, will improve the IQ grade at about the same rate as a 2.6 gpa with 64 WE, or a 3.4 gpa with a 36 WE.