I just proved out some of the concepts I talked about above. I was on my way to work today in a rain storm, the first in several weeks, and was doing a gentle turn on my Stratus recumbant in a parking lot (which connects to a bike path), when the rear wheel skidded out on me. I went down on my left side, and skidded about 10-15 feet (traveling 10-15 mph initially). I kept my hands on the handlebars (above-seat steering, or ASS in recumbant language), and tucked my left elbow as I went down. Result: one small abrasion on my left upper forearm, another on my left calf, a slight scrape on my upper thigh, and that was it, injury-wise. It was about like sliding into second base when I was a kid. I was feet-first, on my left side. I left a trail of what appeared to be soap suds where I skidded; the asphalt had recently been refurbished, and was very slick. My chin was tucked, but my head did not come close to contact with the asphalt.
I am glad I was not on my upright bicycle for this event, as the injuries would have been significantly worse. This is how I broke a rib about ten or so years ago on an upright bicycle.
John