How do I achive a Horizontal Spacing 70/30 (%) Split in Card (for it's display)?

Effectively i want a card to grow/shrink as they do already with Home Assistant/Lovelace, but i want the card to keep this form:
HA-70-30-layout

I can 100% achieve my goal through the browser and just changing the first custom:button-card css flex element to 3 1 0px from what it’s element is fixed already to (1 1 0px). Everything looks absolutely perfect (it may not be a 70/30 split, but it looks close enough).

I installed the card-mod frontend extension and added this to my configuration without luck:

      - type: custom:vertical-stack-in-card
        horizontal: true
        style: |
          button-card:first-child {
              flex: 3 1 0px
          }

With the above, the entry gets created properly on the page, but it can’t over-ride the flex: 1 1 0px fixed to the element itself i want to change.

Does anyone know how i can achieve this goal?

Thomas Loven’s layout-card.