I think there are a lot of possible improvements here. I think you know most of those here are Bonneville /SCTA racers and think in terms of SCTA rules for running in venues governed by them. FIA/FIM may well be way different and allow other formats of construction. A streamliner in the former setting requires minimum 4 wheels (can have more) but they do not need to be in rectangular configuration. Your vehicle is looking more like a motorcycle streamliner. As has been stated if your eventual goal is just a wheel driven vehicle run somewhere for the ultimate wheel driven record, you are not bound by SCTA rules. Bolivia comes to mind.