readings were

cn9's= 5.9
cn8's=5.71
cn8'8-j5's=5.49

now gi strings are 4.5

All those voltages are fine for an early sega / data east. even the 4.5v on the strings. I just did a test on a last action hero that has the same G.I setup. all the voltages you have given me are very close to what I have . The machine i tested these voltages on has good g.i lighting.
There are only two things left it could be A, the lamps are 47's instead of 44's or you have a problem with the lamp sockets.

I will do a test on bretts sega just to make sure it equals yours