VR hand rig retargeting issue

Ok I have some trouble make custom model of hand work with UE4 VR hand rig
Basically I am using same rig which is adjusted (note1 : I did clean rig before skin to it , unreal one have some junk rotation values , note2 : I did try to use it as is but still there are some areas that doesn’t translate correct ) to fit custom model I build and everything is perfect until one of animation is apply in which case rig flip or do some weird thing
Is it possible to use UE4 build in retargeting system with just hand (I haven’t able to make it work so far) as it have only preset for humanoid rig , is it possible to make arm rig preset ?
Any advice will be helpful so if you know how to fix this let me know