yeah there's 3 BRs and it's a different sheme from what you are using Martin atm ( i did 20.99 with the technique you explained and there's like 2 tenths to cut in order to get the perfect laptime with those 2 BRs.)
But we can race faster with 3 BRs : get the normal route and when you approach the 1st difficultie ( hard right curve ) you boost, BR and land before the begining of that narrow section.then at the top of the narrow section ( where's there's 2 BPads in semi diagonale) you hit one of them ( mostly the right one) up your nose and BR get the 3 BP in diagonal and then the last BR and be as close as possible of the inside right on the last curve.
The boost and BR is really tricky to use, i constantly hit walls and walls but got a promising 21.05 with that technique.

Ill copy and paste that into the tips for HD