On Monday I finally made some progress with stringing my berimbau! The bottom third of the verga is very thick, so for the last week I had been struggling with it, despite trying different angles and techniques. But after practising for a while, using the method a friend had shown me, I was able to bend the verga far enough to string it so tight that there was some space between biriba and arame to move a small stone back and forth a little.
I think it should be a little tighter still, because the cabaça sits a bit too high (not visible in this picture, as it was taking at an angle from slightly above) and I would like a little bit more space to move the stone. But it made some nice ding-dong-dong sounds already :)