Just thought I'd post a pic of what I've been running this winter. Someone mentioned these screws, but I don't think they posted a picture. The cutting bit is harder than wood screws.
I searched ebay pix and bought the largest headed, smooth edged screws I could find in 1/2" length. I have 42 (~2") in the front and 105 in the rear (~3/4") (more next winter, mostly to distribute the load).
I make a hole from the outside with an ice pick, then I PUSH the screw in, in an effort to avoid cutting any chords. The threads don't provide much grip. I just screw it in till it's all the way against, don't spin it. I then run 60#+ pressure, and 2 extra tubes as liners.
I've run Kold Kutters in ATVs and motorcycles with excellent results, and tried them in my bicycle, but couldn't keep them. The tires were to soft and thin.
Our roads are ice all winter, so I seldom ride on pavement even crossing the road.
Problems? More than a few inches of snow becomes a problem (I can carry it out, unlike the snogo and ATV riders). I ride the local ungroomed snogo trails, and the front tire tends to follow ski tracks in loose snow. Not at all sure more studs would help much. On ice the front has enough traction to almost lift the rear tire when braking. To much throttle will lift pressure from the front and it slides (same as in summer). The studs, coat, and snow pants, but especially deep snow REALLY draw current. Riding trails I occasionally use more than 100wh/mi.
I rode to and from the post office (5mi) a few days ago, on ice with drifts of 2" or so. I had no trouble at speeds over 20mph in spite of 30mph+ crosswinds with 50mph+ gusts. I was leaning at maybe 20 degrees at times, but had no problems (I stayed on the downwind side of the road, though).
I didn't fall once all winter! When riding that is.
Bob