It took three people and 3.5 hours (most of it filling up the staircase so we could place the ladder somewhere), but finally the clock is mounted where it was planned.
In the end it worked quite well and no one died in the process. We really tried. 
One of our constructs that failed. We needed to be higher and more to the right:
[ATTACH=JSON]{“data-align”:“none”,“data-size”:“small”,“data-attachmentid”:7581}[/ATTACH]
In the end all three holes finally were drilled into the wall, at the right places and the clock is up and not running as I need to finish the wiring.
For today I am done.
To fill up the staircase we used: 8 car tires, 2 palettes, 14 bricks, 16 50x50 carpet floor tiles, a small tool cabinet, an unopened box of carpet floor tiles, some random 40x50x12mm wooden plate, some cutting 20mm board, a 4 meter long power cord as security wire to prevent the ladder from falling, a four segmented 4 meter ladder and three people to lift it up to the centered hook I mounted in advance. Later more stunts where required to drill the holes for the left and more dangerous the right wall hook.
This was fun and Tetris on max level.
[ATTACH=JSON]{“data-align”:“none”,“data-size”:“small”,“data-attachmentid”:7582}[/ATTACH]
On the top left you can see the closed electrical wall box, which I taped the extended wire from my door bell onto, so it was out of the way. The door bell will be placed on top of the clock and probably integrated, so the clock face also shows/blinks “door”, when someone used the bell. The power cord will be routed to the main power box, too. The dangling plug is just from testing on my workbench.
