Your TV supports the follow resolutions:
Signal name Horizontal frequency (kHz) Vertical Frequency (Hz) 640x480 @60Hz 31.47 60.00 1280X720 @60Hz 45.00 60.00 1920X1080 @60Hz 67.50 60.00
If you try to tweak the OSSC, I think you should base on this.
Here the manual of the Panasonic TX-P55VT50Y. See page 115.
Hope it helps.