Serial1 increase buffer size Photon

Hi, I need to increase the Seria1 buffer size (64 bytes) in the Photon, as i did it in the past with Spark Core. Regarding this subject I have found some similar issues, 21435 and 25770.

But still i have not certain if is possible or not to increase it! I have tried to increase SERIAL_BUFFER_SIZE from 64 to 256 in the “usart_hal.h” in the last firmware release 0.5.3, but without success, the buffer stills overrun at 64bytes.