For the life of me, why is there not a way to include the below defines# into the sketch and have the arduino core adjust the serial buffers during build:
SERIAL_TX_BUFFER_SIZE 
SERIAL_RX_BUFFER_SIZE 

There are multiple options for "Configure IDE Locations" which change where the HardwareSerial.h is located. If new versions of the Arduino software are installed, manually declared #defines are replaced.

A secondary question is: where are the core files stored when set to Visual Micro (NO IDE) ?

Note: I'm using a non-preemptive interrupt board atmega2560 and have critical hardware events which may delay serial port processing, hence the reason to increase buffer size.

Thanks

Thanks you so much Simon 

This is exactly what I was looking for. You may want to put a note on this in the FAQ page for defines as it pertains to buffer size.

If you look at the Arduino forum, its just a cat fight on how you should handle serial data better. I will make sure I make a mention on their site how VM has a very clean way to handle this. 

Happy Holidays...