I was once severely caned with a piece of fiberglass tubing. I learned that this type of cane is only for those who like deep and I really mean deep pain!
Because of the thickness and flexibility of the rod the welts were not too bad (only about 10 days to disappear), but the internal bruising was paralizing. I could still feel the effects of a baker's dozen after three weeks
The added bonus was the wickedly shrill whistling sound that preceded each stroke (air escaping from the tube's interior at an awesome speed). To this day just the thought of that sound sends a shiver down my spine and an electric shock to my pussy