Might work, I forgot how I did mine when I was using it to get it into the right position. However I do remember it was still sitting against the backing plate. try mounting it the normal way but just turn it so it points infront of your chin when standing normally.
Angle looks about right mate, although I found its better if you put the mount the other way up then hang the GoPro upside down from it. Just keeps the weight over the chest mount plate and and not flapping about underneath it.
it's personal to your body/position on the bike, so set it up to point forward when you're in 'attack position'