Expose 2 parameter to adjust the height and width.

[Shiba-Kar]

return Scaffold(
          appBar: AppBar(
            backgroundColor: Colors.transparent,
            elevation: 0.0,
            title: Text("WALLET"),
          ),
          body: Column(
            children: [
              Expanded(flex: 1, child: Container(color: Colors.green)),
              Expanded(
                flex: 2,
                child: Container(
                  // color: Colors.red,
                  height: double.maxFinite,
                  width: double.maxFinite,
                  child: CreditCardSlider(
                    _creditCards,
                    initialCard: 1,
                    percentOfUpperCard: 0.60,
                  ),
                ),
              )
            ],
          ),
        ); 

This simple code makes the cards to shrink and overflow by 28px