Scott, I've found if it's all the way to the right the breathing on exhale is very hard, but it doesn't burp bubbles as much. Conversely, all the way left is very easy breathing but exausts more bubbles. I generally set mine in the middle, about 3 clicks, and it is a happy medium. I've also found that regardless of the OPV settting, deep exhalelations are gonna burp off bubbles so my thinking is why make it harder to breathe than necessary? During the dive I will intentionally exhale very deeply a few times to make the OPV purge. That lets me know at depth that it's working properly. Hope this helps. FD
