I have used my own MAX7129 with a 3 digit 7-segment for my IAS/MACH display. Everything powers up perfectly, with the digits in the right place (o=0 in data.cfg), however, the display is in reverse.
For example IAS of 123 displays as 321 on my 7-segment.
This is likely to be me with bad design of my PCB, but is there a configuration "trick" I can do to reverse the output to make 123 = 123 !! :D