Those are the last 2 short cuts I found!
The other 3 are:
on the first curve ( the rounded one, not at the top where you found yours ) you can cut through just under the house and then turn left up to the 1st check point.
The next one I found is a nice savings. At the top, just after the check point, you can go through just north of the house.
In fact, using your top of the screen short cut, you could almost go straight though, but a bush blocks you at the check point.
With a quick wiggle, you can go right through. I still crash some of the time..LOL
The last one is not nearly as good as your bottom one, but still very good.... but hard to do.
On the down swing just past the second check point, you can do a HARD right just north of the house and cut through the next up road and then turn left on the last
down angled road headed to check point 1.
On the image attached:
Yellow... may be slower ( long cut! ) and it is hard to do.
RED is a game changer and it can be linked to GREEN easy enough ( crashed 1 out my 2 attempts )
BLUE saves some time, but it has SLOW grass involved and it is a hard turn.
BROWN at the bottom, again, a game changer. Easy to get through and make the turn north.
I have not had a chance to play again using Red, Green and Brown...... But I am thinking 2:45ish
As I wrote the top part, I was not sure it was understandable, so I drew the map with color coded lines.
Now I think they are to small, but I hope they are okay.
Now, I will have to look at the other courses!
I hope this doesn't spoil the game for others. But it was kind of cool to find these!