After Effects - Green Screen - Non keyed, overlapping areas make final result look bad

Question

I'm working on a fitness video that was filmed in front of a full body green screen.

Most of the subject's body is in front of the green but some of her body overlaps the gym mat.

When I key out the screen and shrink the edges, only the area in front of the screen is being affected (as you would expect).

The only problem is, the area of the legs in front of the screen become slightly narrower than the area of the legs in front of the gym mat - quite noticeable in the final result.

Is there a trick to help prevent this?

Here is a (zoomed in) image of what I'm dealing with. The arrows indicate narrower vs. wider areas of the legs:

I'm following this YouTube tutorial:

Answer 1

Try using the advanced spill suppressor preset technique instead. I’ve found it to work better but take longer to render:

Answer 2

That's a tricky one. Here's one dirty solution I want to propose:

Apply a second keyer for the red hue of the gym-mat. Now shrink your alpha just like you did with the greenscreen. Then, you could stitch together a patch for the mat (effectively a clean-plate of the mat without the legs). Next, track your footage, put the gym-mat-patch behind her legs and apply the tracked motion to the patch. This should give you equal matte-chokes across the legs.

Answer 3

Another thought- the problematic area is very dark. Maybe you could use Extract to make a second key, a bit like a luma key, keeping the black leggings and removing everything else, then overlaying a masked section just where the problem occurs?