Thank you Andy & Lorellei.
When you blacken fish (or anything), it's not the flesh that's blackening, it's the spices, more specifically the paprika. K-Paul used thin filets of redfish or pompano, so a couple minutes of cooking was all it took to both blacken the paprika and cook the fish through.
If you are using anything thicker than about a half inch, it will blacken beyond the paprika and actually burn the flesh before it gets cooked through. That's when you get fire alarms in the kitchen. Even Paul says in his recipe that for thicker pieces, you need to turn the heat down. You need to give it a chance to cook through before you go from black spice to burnt food. I was using a nice thick piece of halibut, so I backed off on the heat.
I would have liked to take it a step darker, but the fish was cooked through and there's nothing worse than overcooked fish!
As far as the spice blend, most are all pretty similar. Most recipes call for sweet paprika - since I usually cook it on the stove instead of over flame, I think the smoked paprika adds something otherwise missing. I rarely have white pepper on hand, so I just increase the black pepper. I know that white pepper adds a certain 'fruitiness', but it doesn't keep its pungency for long, so I usually don't buy it.
I remember when we often had longer discussions like this on a topic, with all our different experiences. Daily dinner is nice, but these threads are what made the forum fun.
Oh, and my picture is turned sideways for some unknown reason. I guess I forgot how to upload it correctly.