I like NaBUru38's drawing, with a turn 7 of the second one, and turn 11/12 of th second.
The chicane at 9/10 should be taken out and the cars have a long sweeping flatout backstraight IMO. Course seems alittle short at 2.3 miles, but more laps so I guess that's good.
To lengthen it, I'd say add a fast extension sort of like Road Atlanta. Go straight at turn 13 going up the hill, going over the paddock road, possibly alittle scenic woods drive, hairpin and chicane right before pit entry and rejoining the track for turn 15.
I think those would make the current track better, aswell as adding an extension that is good to watch the cars full throttle, and probalbly 2 good passing zones.
I also think that this track is suitable for F1 competition, obviously it needs garages, bigger grandstands, and probalbly a wider (and longer, bring turn 15 back alittle possibly, could create another passing zone aswell) front straight. If the FIA thought the track part was 'unsafe' I don't think it would have recieved 1T.
Anyways, don't think these changes will be made. Maybe a few turns tweeked and a road added at 9/10 to take it straight, but that's all I realistically think would get done. Shame because I would love a USGP here.
