If you do a search for "levitation holds," you can find some previous discussions on it. (note spelling, otherwise you won't have any results!)
I don't think you need to be able to do them like Cathe to get the benefits (she even says that just trying is good). Instead of looking at Cathe (who can do everything!) look at Rhonda and Brenda (who are also in fabulous shape). They don't have their feet off the ground all the time. It might be easier for smaller people with smaller lower bodies (Brenda has strong legs, and Rhonda is around 5'6" while Cathe and the others are near 5'2").
I found that I have no problem doing them while seated on my acupuncturists padded table. I stay in "chair" position, then can lift myself up either grabbing the front edges of the table, or splaying my fingers on top of the table (Cathe and crew use the splayed-fingers move) or going up on my knuckles. I lift my whole body weight, and can hold it for a count of 10, but it's in a different position than on the floor with the weight of my legs out in front of me.