Theme: No Standing - Sit anywhere.
20A. *Mattress support : BOX SPRING. Box Seats.
39A. *Light, friendly punch : LOVE TAP. Love Seats.
56A. Spots for airline magazines ... and, literally, what the first words of the answers to starred clues can all have : SEATBACKS
11D. *Wishful lifetime agenda : BUCKET LIST. Bucket Seats.
27D. *Slapstick slipping cause : BANANA PEEL. Banana Seats.
Argyle here. One problem I anticipate is certain anons will have a nit field day.
Across:
1. Potato bag : SACK
5. Rod in a grill : SPIT
9. Macaroni shape : ELBOW
14. Vintage soda : NEHI
15. Chisholm Trail city : WACO
16. Red, in roulette : ROUGE
17. Mine extracts : OREs
18. Club used for chipping : IRON
19. Capital of Ghana : ACCRA
22. Spoken for : TAKEN
23. Skinny fish : EELs
24. Quick message : NOTE
25. Blue Ribbon beer : PABST
28. Palm Pilot, e.g., briefly : PDA. (personal data assistant)
30. Carve in stone : ETCH
33. Attributive menu words : À LA
34. Parisian partings : ADIEUs
37. Leave rolling in the aisles : SLAY
38. Sermon topic : SIN
41. Sitter's handful : IMP or 63A. Sitter's handful : BRAT
42. What some missiles seek : HEAT
44. Stevenson title doctor : JEKYLL
45. "I warned you!" : "SEE!"
46. Gothic fiction author Rice : ANNE. The Vampire Chronicles.
47. WWII espionage gp. : OSS. (Office of Strategic Services)
48. Bugs and Jags : AUTOS. Volkswagen and Jaguar Land Rover.
50. "Fire" bugs : ANTS. Fire ants.
52. Bourgogne and Chablis : VINs. French spelling of regional wines.
54. Longstocking of kiddie lit : PIPPI. Another red-headed girl but not like Anne of Green Gables.
61. NBA great Shaquille : O'NEAL
62. Footnote "p" : PAGE
64. Modern mil. treaty violation : N-TEST
65. Egg cell : OVUM
66. Humdinger : LULU
67. Knuckleheads : DOLTS
68. Short- or long-sleeved tops : TEEs
69. Marked, as a ballot : EXed
Down:
1. Stereotypical "Dahling!" speaker : SNOB
2. Flight-related prefix : AERO
3. General Mills brand : CHEX
4. Affectionate greetings : KISSES. Air kisses, Dahling.
5. Marble cake pattern : SWIRL
6. Capital on the Seine : PARIS
7. Pic to click : ICON
8. Grab from the grill, as a hot dog : TONG
9. Poetry Muse : ERATO
10. Tracks down : LOCATES
12. Storybook brute : OGRE
13. Withdraw gradually : WEAN
21. "He loves me" piece : PETAL
24. Sounding like one has a cold : NASAL
25. Old Turkish title : PASHA
26. Otherworldly : ALIEN
28. Sneaks a look : PEEKS
29. Obligation : DUTY
31. Typical Hitchcock role : CAMEO
32. Publicizes aggressively : HYPEs
35. Martial arts schools : DOJOs
36. Currier's colleague : IVES. Millard Fillmore's?
40. Backup strategy : PLAN B
43. When the big hand is on two : TEN PAST
49. In working order : USABLE
51. Leans slightly : TILTS
52. Beating around the bush : VAGUE
53. Agenda bullets : ITEMS
54. Common koi habitat : POND
55. Look __: investigate : INTO
56. Washday woe : SPOT
57. Nesting site, perhaps : EAVE
58. Essence : CRUX
59. Leafy veggie baked for chips : KALE. Baby Blues/Rick Kirkman and Jerry Scott/Jan. 10, 2016
60. Gym specimen : STUD. How to find a stud.
Argyle