I like my heavy British poncho. I have a carradice Duxback rain poncho (Super) which is about 1kg.

As for poncho problems, I have had only one going down hill at about 30mph I was hit by a hard gust that pushed me over two lanes on the road. I slow down to 15-20 and had no more gust problems. That evening I looked up the weather which said 20-30mph wind gusts.

When wind is 10 mph or higher I tie the waistband and put loops over my thumb and wrist instead of loosely attached to my handlebars by the brakes.