You might not experience the side effects with the greatly reduced dose, but start to notice them as you increase the dosage later on. When I started Beta 14 years ago I started out with the full dose (doctors didn't do the low dosages thing then), and it took about 2 months for the side effects to subside. I hope you continue to experience few side effects.
Still after 14 years I'll experience them occasionally, maybe 3-4 times a year. Usually it will happen when I'm overtired, or sick with something else, like a cold. But I still always take a couple of ibuprofen at the time of my shot (bedtime), and then sleep through the night.