POV Kit will not fully function with Capture v3 because we removed the plate lock feature. Previous versions of Capture had an additional locking screw on the opposite side of the quick-release button. The screw secured the plate into place and prevented jiggling. This feature was only useful when mounting a GoPro. The rest of the time, the plate lock screw would tend to dig into your shoulder or waist, making it uncomfortable. Hence, we removed it.
We are developing an updated piece of hardware for POV Kit that will contain a stabilizing screw in it. This will let you use POV Kit with Capture v3. The good news is that if you already own POV Kit, you won't have to get a whole new kit. You can simply get the replacement part. Here's a rough 3D printed prototype, followed by a rendering of a near-final design:
We're actively developing this POV Kit update and it probably won't be ready until the first few months of 2018. So, if you have POV Kit (or you're interested in GoPro mounting) and you want to be notified when the update is available, signup on our POV Kit Notification List. We're not sure what the upgraded hardware will cost, but we will be sure to give our existing customers and backers a special deal on it.