Adding more memory to Serial (0) for larger buffers

Hey I am wondering if there is a way to add extra memory to "Serial" zero for reading and writing just like the following for Serial1? (Yes I know it is very fast already and runs at 480Mbaud but every microsecond counts and I don't want to block waiting for writes if possible)

 Serial1.addMemoryForWrite(radio_tx_buffer, sizeof(radio_tx_buffer));
 Serial1.addMemoryForRead(radio_rx_buffer, sizeof(radio_rx_buffer));

Sorry, I don't believe that is possible. AFAIK - it is only implemented within HardwareSerial,
(and maybe FlexIO Serial)...

My guess is you can probably edit the source code, to allow for larger count of buffers:
like usb_serial.c

Where you see the defines:
#define TX_NUM   4
#define TX_SIZE  2048 /* should be a multiple of CDC_TX_SIZE */