Following the above I've done a thorough check of four aircraft fitted with identical kit and below are the "Radio Stack" lines from the panel.cfg of each:
MD83 DC10
[Window03]
file=radio_a.bmp
size_mm=1024
position=0
visible=0
ident=RADIO_STACK_PANEL
gauge00=737-400!Comm 1, 650,432,204,50
gauge01=737-400!Nav 1, 650,481,204,50
gauge02=737-400!Nav 2, 650,530,204,50
gauge03=737-400!Transponder, 650,579,204,50
gauge04=737-400!ADF, 650,628,204,50
gauge05=737-400!Audio, 650,677,204,23
Boeing 737-400
[Window03]
file=radio_a.bmp
size_mm=1024
position=0
visible=0
ident=RADIO_STACK_PANEL
gauge00=737-400!Comm 1, 650,432,204,50
gauge01=737-400!Nav 1, 650,481,204,50
gauge02=737-400!Nav 2, 650,530,204,50
gauge03=737-400!Transponder, 650,579,204,50
gauge04=737-400!ADF, 650,628,204,50
gauge05=737-400!Audio, 650,677,204,
Lockheed L1011
[Window02]
Background_color=0,0,0
size_mm=127,319
window_size_ratio=1.00
position=0
visible=0
ident=RADIO_STACK_PANEL
window_size= 0.250, 0.650
window_pos= 0.000, 0.350
gauge00=737-400!Comm 1, 0,0,127,54
gauge01=737-400!Comm 2, 0,54,127,54
gauge02=737-400!Nav 1, 0,108,127,54
gauge03=737-400!Nav 2, 0,162,127,54
gauge04=737-400!Transponder, 0,216,127,49
gauge05=737-400!ADF, 0,265,127,54
gauge06=737-400!Audio, 0,319,127,26
Lockheed C130 Hercules
[Window02]
Background_color=16,16,16
size_mm=127,345
position=8
visible=0
ident=RADIO_STACK_PANEL
gauge00=737-400!Comm 1, 0,0
gauge01=737-400!Comm 2, 0,54
gauge02=737-400!Nav 1, 0,108
gauge03=737-400!Nav 2, 0,162
gauge04=737-400!Transponder, 0,216
gauge05=737-400!ADF, 0,265
gauge06=737-400!Audio, 0,319
I measured the dimensions of the Radio Stack for each on my 17" screen:
DC10 : 3.75" high x 2.6" wide
737 : 7.5" high x 2.5" wide
L1011 : 6.5" high x 3.5" wide
C130 : 5" high x 1.75" wide
The DC10, 737 and C130 all show the Audio Panel but the L1011 does not.
I note the difference in the lines above the "gauge" info but I can see no reason why the L1011 should lack the Audio Panel - I wonder if you can see what I am missing?
rgds