QTR-Quadtone RIP

Hi all,

I've been printing with paul's curves on Photorag for a whil now, and I'm trying new papers. Since I do not have any spectro, I tried to linearize my profile with my Epson V500 scanner.
I did it this way:
1. Printed a 21 step strip on Photorag with Paul's curve, let it dry.
2. Scanned it (tif, gray levels)
3. adjusted the picture (with Gimp) to get the white square at 100% and the black one at 0%
4. adjusted the gamma (1.3), to have all squares (or nearly) at their normal value (100-95-90-85-...)
5. Printed same strip on new paper with non linearized curve, let it dry.
6. scanned it with same parameters as 2.
7. adjusted it: black, white, and gamma to 1.3
I got the following values: 100-96-90-84-79-72-65-62-60-53-47-45-40-34-27-23-21-19-15-9-0
8. I put the values in QTR for linearization.
9. Printed a new strip to check. Bad result. Seems to be too much corrected.

Question: what did I miss?

Help!

Thx :o)