@tkln I guess, that's not doable right now, but you could try sensorless homing for one of the motors on each tower.

@dc42 thank you I got it working. For those who might come later in this post here is my config for reference :

M584 X0.0 Y0.1 Z0.2 A0.3 C0.4 E0.5 U1.0 ; set drive mapping M669 K0 X1:0:0:0:0:0 Y0:1:0:0:0:0 Z0:0:1:0:0:0 ; set kinematics parameters M669 K0 U0:0:0:1:0:0 A0:0:0:0:1:0 C0:0:0:0:-1:1 ; set kinematics parameters