Crossword puzzle clue "they're hard in across answers and soft in down ones"

They're hard in across answers and soft in down ones

Letter appearing only in down answers; its opposite appears only in across answers

Soft rock found in the eight longest Across answers

Athletic infraction ... or what occurs at the beginning of this puzzle's four theme answers, both across and down

They can be found in six long Across answers

1980 William Hurt film (and what eight answers herein contain on a trip across the country)

Illegal concealment ... and a hint to ten Across answers in this puzzle

Track mix for a party, and what the five longest Across answers comprise