Particle System's SetStartPoint doesn't stay relative to actor

I have a particle system defined through the normal visual interface. I’m loading it inside of an actor, attaching it, and trying to get the start and end points to stay relative within the actor’s coordinates, but no matter what I do they stay in world coordinates.

UParticleSystemComponent *beam = NewObject<UParticleSystemComponent>(this, FName(*(name)));
beam->AttachToComponent(RootComponent, FAttachmentTransformRules(EAttachmentRule::KeepRelative, EAttachmentRule::KeepRelative, EAttachmentRule::KeepRelative, true));

// Loaded in the actor's constructor

// The beam is correctly transformed along with the actor when these are set!
//beam->SetActorParameter("BeamSource", this);
//beam->SetActorParameter("BeamTarget", this);

// ... but not these
beam->SetBeamSourcePoint(0, FVector(100, 0, 0), 0);
beam->SetBeamEndPoint(0, FVector(0, 0, 0));

I have my source and target set to User Defined, but I’ve also tried all the other combinations. Not only does the beam not translate its source and target correctly, it doesn’t transform along with the actor (it does appear in the view.)

When I set source and target to be “Actor” instead of “User Defined” the point correctly tracks the actor. I’ve resorted to updating source and target points for each beam in the actor’s Tick method, but that seems sloppy.

Can I attach both ends of the beam to either points in space, components within the actor, or some other relative object such that the beam gets all the transforms from its parent? The mesh for the actor is entirely programmatic, so a c++ solution is ideal :smiley: