Doing a little digging in th e new price charts effective June 23, 2019. Here is a link to the PDF:
https://pe.usps.com/resources/PriceChange/June%202019%20-%20Notice123.pdf
Verbiage from the PDF regarding retail ground:
1. Zones 1–4 are only for the mailing of hazardous materials, live
animals, or other items required to be shipped by ground
transportation (does not apply to oversized parcels).
2. For parcels that measure in combined length and girth more than 84
inches but not more than 108 inches, and the piece weighs less
than 20 pounds, use the 20-pound price (balloon price) based on
the applicable zone.
3. For parcels that measure in combined length and girth more than
108 inches but not more than 130 inches, use the oversized price,
regardless of weight, based on the applicable zone.
(This is on page 8 of the PDF)
Verbiage for parcel select:
1. IMpb Noncompliant Fee $0.20 per piece.
2. For parcels that measure in combined length and girth more than
108 inches but not more than 130 inches, use oversized prices,
regardless of weight, based on the applicable zone.
3. Parcels that exceed one cubic foot (1,728 cubic inches) are charged
based on the actual weight or the dimensional weight, whichever is
greater (as calculated in DMM 253.1.3).
(Page 25 of PDF)
So how I read it, you cannot use retail ground in zones 1-4 unless it is an item that has to shipped by ground, except for oversize parcels. But for zone 5-9, it would seem that dimensional weight will not apply.