Spawning a child object with UNET

I've recently started adding co-op to my game using UNET, and I'm having real problems getting my head around it.

I'm currently just trying to set up a simple test scene.

• I have a NetworkManager in the scene.

• I have a prefab for the player, with a PlayerActor component based around NetworkBehaviour, as well as a NetworkIdentity with local authority enabled; this is registered in the NetworkManager as the player prefab.

• I've also got a prefab with a WeaponActor and NetworkIdentity component on board. This is registered as spawnable.

All I want to do is provide the ability to add and remove instances of the WeaponActor prefab as a child of the PlayerActor - (I'll need local authority on the weapon, but I can come back to that..)

I've tried both of the approaches detailed here, but neither of them seem to be working properly for me. I just don't seem to be able to get this working at both client and host at the same time.

 public class PlayerActor : NetworkBehaviour
 {
     [SerializeField]
     private GameObject weaponPrefab;
 
     public override void OnStartLocalPlayer()
     {
         this.Cmd_WeaponSpawn(this.weaponPrefab);
     }
 
     [Command]
     private void Cmd_WeaponSpawn(GameObject weaponPrefab)
     {
         GameObject weapon = Object.Instantiate(weaponPrefab);
         weapon.SetParent(this);
 
         NetworkServer.Spawn(weapon);
         this.Rpc_WeaponLink(weapon);
     }
 
     [ClientRpc]
     private void Rpc_WeaponLink(GameObject weapon)
     {
         weapon.SetParent(this);
     }
 }

The specific problems vary, from Failed to spawn server object to the prefab being null, but most often methods simply not executing.

How should I do this? Do I need to fix the above or switch to an entirely different approach?