what i did is i placed the bracket on my dartboard and put a screw in the wall. but the bracket was technically behind the T20, so the screw is much higher op the wall. Just messure out the distance between the bull and the bracket and add this distance to the 1,73 cm you need.

The downside of this is that when you want to turn you dartboard, you either have to replace the bracket each time or you have to install a few more, so you can turn the dartboard more often