I have currently a concert ukulele that I'm not using and I would like to put on it steel cavaquinho strings in order to use it as a cavaquinho. Is it a bad idea ? Are there risks for my instrument ?
It's always a bad idea to put steel strings on an instrument not designed for them.
The tension is a lot higher than nylon & could result in a bent neck, the bridge coming away or at worst a broken headstock or neck.