So next weekend I'm planning on brewing a stout with my brother-in-law who is just starting to get into brewing. He's done a couple of batches with me before and he has enjoyed it and now wants to get more adventurous. He's a big stout fan, and mentioned that he had picked up some oak spirals which he is using in a wine he's making. He has extras. I was thinking I might use them in the stout we're making, possibly soaking them in some bourbon before. How much is too much on that? I don't want an overpowering flavor, just something subtle.