So, i have done a little hologram system. I made a viewportframe. That moves the camera as the players camera. And put it on the entire screen with a backgroundtransparency of 1.
You’re running into an unsolvable limitation of ViewportFrames. Remember that a ViewportFrame is intended to be drawn on the user’s screen whereas the literal viewport (where your character exists) is in the 3D world. Guis render on top of the world; by nature of this, so does the viewport of a Gui.
GUIs are meant to stay on top of the screen. What you can do is use a model with CanCollide of all parts turned off.
If you need it to only show for one player, then either 1) use a localscript to add the model to workspace from like replicatedstorage, or
2) have the model in workspace with all parts transparent (and iterate over it with a localscript to make it visible)