The best I've found so far has a one letter repeat

 T Y M P
 H A I L
 U N C O
 S K E T

With the caveat that

"tymp" does no appear at dictionary.com but does appear on Merriam-Webster. I hope this is acceptable.

I'm not sure how to score this (maybe OP can advise).

The best I've found so far has a one letter repeat

 T Y M P
 H A I L
 U N C O
 S K E T

With the caveat that

"tymp" does not appear at dictionary.com but does appear on Merriam-Webster. I hope this is acceptable.

I'm not sure how to score this (maybe OP can advise).