Parallel 8-bit width in video mode

Hi, 

 My board is based on dlpc350.

  Now, my board is 24-bit width parallel interface: P1_A[9：2];  P1_B[9：2];  P1_C[9：2];  P1A_CLK, P1_DE, P1_VSYNC, P1_HSYNC.

  It works in video mode.

  But I only need grascale projector light.  So  I want to delete P1_B and P1_C to reduce PCB size.

  How should I set registers of DLPC350?

Thanks!