Tablet/phone holder for stationary bicycle

I wanted to listen to some music or watch video while riding the bike. This holder is the result. It can be improved: some springs could be put on the threaded rod.
File names and most of the comments are in Hungarian in .scad files... sorry.
I used 2x0.5 meters M8 threaded rod and M4 bolts and nuts.
8 top and 8 bottom layers were printed with 50% infill. Filament is PLA.