HP HDX9000: black screen problem with GTX 280M

[Remdale]

Hi everyone.
My laptop HP HDX9000 has an MXM slot, but the original card (Nvidia 8800M GTS) is treated as a normal PCIe card. It's not following the MXM software specification.
After inserting GTX 280M, there's no picture on the internal screen, but the OS is booting up fine. Needed to swap LVDS pins before doing that because LVDS pinout in the laptop is not following the MXM hardware specification. The backlight is working fine. But when I flashed vBIOS from GTX 260M, the picture comes on, but there's no backlight. When I flash vBIOS from the 8800M GTS, the picture comes on and the backlight works fine, but obviously the performance and memory amount are low.
I can make GTX 280M not require the MXM structure, but the picture doesn't appear on the screen anyway, so there's a problem with setting up output signal to the internal screen. The card can't probably pick up EDID through DDC.
.NetRolller 3D said a long time ago that MXM structure should be inserted into the vBIOS, but I don't know how to make it all work. By the way, I have written a vBIOS parcer in ImHex for old Nvidia cards, so it's easier to find some needed things in the vBIOS.
Do you have any ideas on how to make the card work with my laptop?