Having issues with blue screen keying - getting color contamination in Advence green screen clean up

I'm working on keying out a product shot of a white/grey shoe with mint green elements. I'm running into some persistent issues with color contamination despite trying multiple approaches.

Current Setup:

• Shot against blue screen (chose blue due to green elements in the shoe)
• Using Keylight 1.2, Key Cleaner, Advanced Spill Suppressor
• Also tried roto brush and various masking approaches

The Problem: When using Keylight, I'm getting green semi-transparent zones in the grey areas of the shoe that I just can't seem to eliminate. These are affecting the color accuracy in my final comp, especially in the grey tones.

What I've Tried:

• Various Keylight settings
• Combination of Key Cleaner and Advanced Spill Suppressor
• Some masking work
• Roto brush 

Questions:

1. Is there a better way to clean up the interior mask areas?
2. Would switching to a yellow or red background work better given the shoe's colors?
3. Any suggestions for preserving the true grey tones while still getting a clean key?

Any help would be greatly appreciated!