How to Green Screen Removal with Custom Avatar

Subject: Green Screen Removal Challenge with Custom Avatar

I'm following your recommendation to use #008000 green screen with my custom Instant Avatar and remove it in post-processing with ffmpeg.

Issue I'm encountering:
When using ffmpeg's colorkey filter, I'm finding it difficult to balance green removal vs. avatar preservation:

Low similarity (0.3-0.4): Green background clearly visible, avatar looks normal
Medium similarity (0.45-0.5): Green mostly removed, but avatar becomes semi-transparent/ghosted
High similarity (0.6+): Avatar disappears completely

It seems the avatar has some green tones that cause it to become transparent when removing the background.

Questions:

Is there a different background color (e.g., blue, magenta) that might work better for chroma keying with Instant Avatars?
Are there specific avatar settings or lighting conditions that produce cleaner green screen separation?
Does HeyGen use any edge feathering or green spill suppression that I should account for in post-processing?
Would you recommend a different post-processing approach besides simple colorkey filtering?

Any guidance on achieving clean background removal would be greatly appreciated!

Thank you!