With the fortezo/PWT youre right, you have to watch like a hawk with selenium to prevent it looking like it has beeen copper toned. I find that using a powerful spotlight on the print as it tones help a great deal to see the effect on colour styarting to build as it opens up shadow detail far more than light of normal viewing intensity. Once a touch of colour is seen it is time for me to pull it. By the time drydown has taken place and the print is displayed under less harsh light, the effect is about right for me.