KCMO wrote on Aug 29^th, 2014 at 2:16am:

Some key combos (shft-5, shft-6, and shft-9) just show a black rectangle so as you suggest the -300 doesn't look to be 100% compatible.

In the topic I mentioned in my previous post, is a link to the modified panel.cfg's that I did to make the 777-300 and 777 Freighter work great in P3D. That way, there should be no black rectangles.

To save you the trouble, here is the link for them: https://www.dropbox.com/s/cfg3vf6vmvxh89m/773%26777F_P3Dv2.zip ;)