After building first prototype X axis, I believe I can win the battle 
This little setup can handle double of weight that I actually need. It can handle 5D mark IV + EF 70-200mm + battery pack, up and down at 90 degrees.
The torque on idle (that came from pulleys reduction and belt friction) is enough to hold my weight at about 60 degrees, without powering up the motor.
The speed is more than enough for what this setup is designed.
No slop, no backslash caused by gearing 
