I have come into the unsavory situation of having to overstuff my channels. Namely I am creating dynamic water ripples and to cut a long story short, I store the dynamic normal data in the R and G channels, the height of the ripple-causer in B (to avoid showing the ripple if the surface is too far above or below the limb causing the ripple) and A is for alpha, as my ripple texture has a smooth fade. I output this as a particle system off-screen, a SceneCapture2D actor set to only capture particles and translucency grabs it and I put it in a render texture. My water shader reads that texture and applies the normal map on top of the rest.
The problem is that I need more info, specifically displacement. I am thinking that it could share the blue channel with the height, half the bits for each. Question is just - how many bits does UE4 store per channel in a render texture with HDR compression… 32?