Found it. Be interested to see folks here try some of these things out:
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First open the panel.cfg in a text editor (it should be in SimObjects\Airplanes\CS_B777-200ER_GE\panel)

Look for sections [VCockpit05] to [VCockpit10], 6 total.

In each of these 6 sections, replace

pixel_size=512,512

with

pixel_size=256,256

This should give a 20% FPS boost, does for me at least.

Make sure while testing that you load the same aircraft for which you modified the panel.cfg. If it looks good you can modify all models of 777 like this.

The 256,256 may make the displays pixelated if you zoom in close. You can try a higher value like 320,320, that's pretty sharp. But some FPS may be lost.

Another thing which you can do is replicate the Pilot's left panels also to the co-pilot side. This will render the same display on both sides. To do this, under [VCockpit07], look for this line:

gauge00=Captain_Sim.x777.display!DisplayGauge,     8, 15, 496,482,5

Change the last digit in this line from 5 to 2

and under [VCockpit08], look for:

gauge00=Captain_Sim.x777.display!DisplayGauge,     8, 15, 496,482,6

Change the last digit from 6 to 1

Now co-pilot's displays will mirror the pilot's and save some more FPS.

And last, if you don't use the EFB or weather radar:

Rename the Captain_Sim.x777.efb.dll and Captain_Sim.x777.wxr.dll to something like *.dll_ so that they don't load.