I tried for a while and then needed to hit the road and put it on pause. I bought a really cheap project to test the concept. I think for it to work I would need to purchase some fairly expensive film to put on the window. My last attempt was getting some perforated window shade material so I could look out. In the end, I purchased a refurbished 12" RCA windows tablet for $100 and mounted that on the left side so it doesn't get in the way of anything. Brighter, closer, works fine. HUD will probably have too many issue to be reliable in all sun and dark conditions.
Back in 2017 I saw a post where you were working with VMSpc and a DIY HUD projector. Unfortunately the thread ended with your post that you were going to work on this in a month when you got home. Did this ever work out? Are you using a HUD. What projector did you use? Any info would be appreciated.