3d helicopter pilot here. Hard to tell on the video but your headspeed sounds a bit low. You could increase it and the tail will lock in. Tails have more holding power at higher headspeeds. Great video man
Just finished building mine and did a quick first flight. Smooth, quiet and stable. Only running a small 2216 2600 kv Xnova and 40A hobby wing. Bought the Xnova 2618 1580 kv but don't have the bigger ESC yet. KST X-12 508 cyclic servos and MKS DS 95i on the tail, Spirit 2 flight controller with srxl2 rcvr. Enjoy your Oxy, they are awesome, this is my second, trying to decide if I want a 500 someday. The guys on HF said no need to buy any upgrades so running all stock parts. However, I may get the upgrade metal tail servo mounts.
Make sure that your tail is set mechanically first, then you change your gain if need be. I think Coeshow said your tail should be like 2 degrees right. Infact I'll just link this video where he explains how to make sure it's set correctly. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-o2ee2VDAENg.html
Setup in normal rate mode for full sweep on pitch slider. When the servo centers you should see the correct amount of offset. Switch to heading lock and Adjust the servo arm length and gyro gain from there....
