There is a little trick that you can do with Sketchup where you can import an image and scale it give a single dimension such as a pit straight
Your Historic GP is 5.516kms or 3.22 miles
in comparison your club circuit ** is 1.155km or 0.72 miles
The Straightish section that you have a pit lane against is only just over 300m with the pit lane being even shorter and no paddock space.
My point for doing this is to say that when thinking about a circuit, one thing you always have to keep in mind is some sort of scale. Even with pencil drawing, perhaps even more so.
When drawing a circuit do you think of the pencil line as the track width, or as the centre line?
Not a trick question,
If it's the width, then you then have a scale ... so for example a hairpin, you wouldn't want the approach and exit virtually touching because the gap would be less than a track width and the hairpin would look like a street circuit hairpin you dislike so much.
If it's a centre line then you have to think how close to I make centre lines pass one another. Parallel: Half a track width, a bit of grass, a barrier, an access road and then the same again on the other side.
Don't get me wrong the Historic circuit is not a bad circuit and just needs a bit of detail work to make it workable, and not that much at that.
But for the overall design, in this case I'd say it's overloaded with loops and sections that are not worthwhile.
For example, I haven't drawn it but The oval, the straights might be around 300m (probably a little less), the gap between then would be 30m at most. 15m radius corners at 15 degrees
In the real word the Hairpin at Montreal which realistically is about as tight as you want to go on a permanent racing circuit has an inside radius of 25m
**the club circuit looks remarkably like Brands Hatch Indy before the squared some of the corners.
I hope you take these comments as constructive and I really look forward to seeing your next designs.