FWIW, for the time being I've settled on the following Orion II settings
for the 707 mike:
For normal SSB operation: TX EQ 0, TX Filter BW 2850, LF Rolloff 150, H/W
MIC Gain 14.0, VOX Trip Level 5%, Anti-Vox 20%, Vox Hang 0.60, MIC 50, SP 4
For AM operation: same except MIC 65 and SP OFF.
I don't know if these are optimal, but they seem to work.
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