Here is the modified UTFT library with a newly routed shield for DUE,
all Data pins are routed to PORTC and all command pins are routed to PORTD
only 4 instructions are needed per write strobe.
Filling the screen 800x480 once will take 212ms
Filling the screen 800x480 with an image directly reading from SPI flash using 42Mhz speed with DMA will take 312ms
This should be the maximum ability of DUE as i think should be the mostly optimized.
Of course, any chance to make it faster will be appreciated. ]
The library is here
http://coldtears.lin3.siteonlinetest.com/files/Arduino_DUE_TFT_library.zip