Hi Jeroen,
Wow what a monster - great job!
FYI: Our Firgelli actuators have a 100:1 gearing ratio. It is possible to swap the 100:1 gearbox for a 210:1 gearbox and invert the motor (210:1 gearing makes the motor run backwards). I've done it here on my bench and it works great. But the question is: Will it be too powerful? Double the power and half the speed - something might break.
I am willing to modify our NXT (soon to be EV3) actuators if anyone wants to give it a try. We are unfortunately not allowed to play with Lego at work.
Note: This is not being considered right now as an production option, but it might help out some people on the larger builds.