Chroma key problem

[sebazvideo]

I have a few small clips that consist of me in front of a green screen. The green screen, however, doesn't take up the whole frame, and in some of the clips, the parts of the frame that are not me or the green screen are not very easy to remove with just the rectangle tool in the chroma key effect in Neo Booster. So to make it easier, I opened one clip in Vegas, made a mask to remove the unwanted parts and leave only me and the green screen behind me. I exported it as an uncompressed RGB with alpha channel, and when I loaded in Neo I made sure that the alpha channel was present by putting this clip on top of another, and indeed, the areas that I had eliminated by using the mask in Vegas were totally transparent and I could see the clip in the track below in those areas.

The problem is, when I loaded the chroma key effect to the clip to key out the green screen and leave only me, the green screen is keyed out, but now what was totally transparent became black. I tried all the different settings in the effect configuration, including the ones in the detail area, and there's nothing I can do to get rid of the black. It's as if this effect wouldn't recognize that there's an alpha channel, because I can even use the picker on the black area that is supposed to be transparent and it keys it out, but of course it leaves the green screen and keys out parts of me that are dark.

So, is this because the chroma keyer in Neo doesn't recognize alpha channels, or am I doing something wrong? I also tried converting the uncompressed RGB file to the Canopus Lossless codec and Canopus HQ Online codec with the same results.