National Symphony Principal Bass Robert Oppelt recently put out an analysis of bow arm angles on his excellent website, which can be found at robertoppelt.com.
Robert advocates keeping a fairly straight bow arm when playing the bass, both for French and German bow. He provides great examples of how a straight arm can more efficiently transmit weight and power, and he includes many photos featuring both the French and German bow holds.
If you haven’t visited Robert’s site before, I highly recommend checking it out. He’s got great articles, interviews with other bassists, and stories about his experiences in then music world. Check it out!