I re-installed 4.9.2 again to see if this would allow me to install and run the Infiltrator demo, and it did.
So unfortunately, it was more a matter of smoke and mirrors, camera angles in Matinee to try and create the invisibility effect using a render target, which unfortunately doesn’t really cut the mustard for what I’m trying to achieve, but undoubtedly did an amazing job in that demo, and I’d love to see more 
I played around with depth masks and custom stencils, and I have been able to change how an object appears behind transparency, but cannot effectively get that mask and cull it out, which from a technical point of view, I kind of understand why this is the case, but I do still wonder if it’s feasible to do this without altering the rendering code, and if I’m just wasting my time and energy trying to figure it out.