I do not disagree with any of the comments, so far, but would add that along with avoiding altering the gamma curve, you should also use all the straight video setting for the HVX. The HVX is noisier than, say, a Varicam, but I have had no trouble keying any HVX 720p HD footage in AE Keylight 1.2. No edge crawl, or glistening hair friz. Remember, the HVX uses 1/2″ chips, and an odd pixel configuration to achieve HD, so pushing it to do 1080 is also amplifying the noise.
Recommend using 720/60p. This will give you denser picture info for the keyer to see, but will burn through media at twice the rate of a 30p native recording mode. (-2) detail will help with edge blending and light wrapping. Full body shots biggest problems are the typical areas of lighting where the hardest shadows of feet meet the floor. Recommend “Space Lights” for the entire set, then punch in modeling lights for faces only. Expose the screen one stop under the foreground faces. Rim light, Rim light, Rim light.
When you get to post try to stay away from the Screen Strength control in Keylight.
Good luck.