The gearbox story on 307 is the definition of perfect engineering meeting inperfect reality.

Engineers calculated that each shift costs some time so it's better to have 4 gears with very good engine that has good power over wide revband and therefore less shifts and in the end better speed.
In reality drivers always "felt" they were in wrong gear and changed gears more often, losing time. (can argue that it could work if drivers just "learned" the car, but that could take quite some time)

After a year(I think) they changed to 5 speed gearbox and 307 was relatively competetive even with 2nd rate drivers (Stohl, H. Solberg, Galli) for quite a while. (even though it was bigger than most other cars).

I have no idea how much Nandan was involved in all that though.