Be careful that you don’t end up accidentally staring the plugs/sockets. I wouldn’t go with anything shorter than 30 cm myself. And difference between 30 cm and 50 cm won’t be that much unless you have strong local sources of interference and really bad cable.
If anything going too short could cause more problems.
You're forcing the router closer to the mains outlet and PSU, sources of interference.
You're putting it somewhere it can get kicked and pick up more dust off the floor.
Its the LEAST optimal place for WiFi reception.