Your imagination is playing tricks on you.
When you look at the map above you will see a little white dote about where the 2200m chute would be on the main track. If you add 200 to 300m it would be lucky to take the "new" chute to the bushes up in the top right hand corner.
No. I stand by my methods.
What I did was get a bit of trace paper and trace out the 2200m shute.
Then by using a pin to secure the trace paper, I rotated it such that the chute was superimposed on the course proper.
Then I calculated what 200m was by looking at the markers on the back straight and added this to my rotated chute at a right angle and I ended out in the road.
If I had not used a right angle and followed the existing track I am not significantly in the "bushes" as you call them.
If you wanted to build a chute in the vacant land area at the top right you would have to get council permission to chop down what looks like some of the last existing trees on the course rectangle. I know Sutherland Shire council would tell you where to go.
If the starting gate were located 20 m from the backyard fence of the house that has what looks like a big shed backing on to the course (??stable) then the race would be 2523m according to my calculations.