I have refilled the 1lb tanks for years. Before they came out with the adaptor I made one from a old propane tourch and BBQ adaptor. I have since bought one of the other adaptors.
You do have to be carefull. Last summer I got the brillant Idea of putting my empty,s in the deep freezer for several days. I got my 20 lb tank full and put it in the sun at over 100 degrees for several hours. It filled the 1 pounders really fast. I then put them in my shed. Several weeks later when we went camping I looked at the tanks, they looked like balloons. It was a miracle they did not explode.
Since then I cool them for about 15 minutes in icewater and use a scale. so far it has been working.