Thing is if the suspension works at 4" ride height then lowering the car may well upset the handling. Just because it's lower doesn't really mean the geometry is right for it all to work.
Maybe the only way to run the car lower would be to lift the mounting points so the chassis sits lower, suspension is a minefield and one change can alter other things.

Here's a question:
Those that have got built Roadster, when the car is jacked up at the front how do the front wheels sit?..do they go into positive camber or negative? This one thing will show whether things are ideal or not.