Color reversal films generally do not push or pull gracefully. Weird things can happen to the 3 layers causing some unpredictable results.

That said, IDK if the following is true today but at one time some Ektachrome 100 films were comparable Ektachrome 200 films with 0.3 neutral density dye added to the coating. This dropped the speed from 200 to 100 and gave an incredible increase in sharpness while everything else stayed the same.