4 ohms to 8 ohm speakers?

Yes sometimes a speakers ratings is a average and could very possibly have dips very well below its 8 ohn rating use the ear to be the judge.

Groundhog,

See this recent thread on the same topic. Bottom line is try it and use which ever sounds best. It will not hurt your amp or speakers.

Use of 4 or 8 ohm tap?

Changing from 8 to 4 ohm has certainly made a major improvement.More pronounced bass,more clarity and a more realistic sound.
I hear things that were dubbed before and now it seems there right up front where I hear them perfect now!
Thanks for the info........
Peace