Blending 2 Delta Keyers

The most common problem for full body shots on green screen (in the imperfect world of budget setups), is less light at the bottom of the frame and shadow areas around the feet (usually noisy).

While an acceptable key can be achieved with compromises, better would be to have seperate settings for the top and bottom of the frame. E.g A Nice open matte at the top for hair etc, and a harder clamped out matte at the bottom.

So easy to create and instance of Delta Keyer, and de-instance a few settings, but how can I blend the 2 resulting mattes on a gradient?

I'm looking for something like a channel splitter to split off the alpha from the RGB, do the merge with a mask, and recombine. But I can't see a way to do that.

Any tips?

Well that turned out to be an easy one using Channel Booleans with everything set to FG to blend the 2 DK outputs with a mask rather than a Merge node.