Should I use Impedance 4 or 8?

There is no damage that will happen in using an output transformer into an unmatched load, however the amount of power available will be greatest into a matched load. Ie 8 ohm tap, 8 ohm speaker.

That said, the damping factor of the 4 ohm taps should be almost double that of the 8 ohm taps. That may be the source of your reduced dynamics issue; overdamping of the woofer. The damping factor (output impedance) will interact with the design of the woofer differently, and since there is no clear guidance, as others have suggested, it seems best to pick the sound that you prefer.

Any chance you contacted Raven Audio to just see what they say ??

I have had Raven Audio since 2019 and have been a very happy customer with them responding to every question I have asked..

Hope you enjoy the Black Hawk , I started with that for month then ended up with Osprey for 5 years now have Reflection with Corvus Speakers and luv the sound.

As you know, that lower-imp. tap is reserved for A+B, speakers connected in parallel or the speaker with lower nominal impedance. A good, issue-free amplifier should not deliver drastically different performance between two taps. When connected to 8 ohm rated speakers, the 2-3 ohm tap on my Parasound NC2125 actually generates less heat and performs more effortlessly than the 4-8 ohm tap.

Maybe this answers it but I'm still very confused about four versus eight ohms.

@viridian  does a great job in his second paragraph and the second paragraph has a lot of information in it.  Maybe some further clarification on this important paragraph. Thank you.

i Use the four ohm from my amplifier because I hear things may sound better when those ranges are explored by my speakers. Speakers tend to very quite a bit in the four and eight areas and this adds to the confusion in my tiny mind.

Yep... Try both...Please let us know if you hear any difference. I have done this and could not tell any difference.