I used pneumatics, as well as spring shocks. I can make it work, but only so long as I can maintain pressure in the reservoir. With leaky rubber tubing, that's only a few days.
The only problem is that there's no place for your mech's toes to have proper hydraulics. We don't see the pistons housings on top of the toes, so they would have to be underneath. They certainly can't go through the toe joint perpindicular to the transit axis. They must be underneath, but the angle of the toe to the foot and the low ground clearance of the center of the foot, means that you would need very tiny pistons or pistons with an extreme transit. We can see no evidence of either. As far as we can see from that render, those toe-tips would have to be actuated by a gear chain or other such contrivance.
I would agree there; that section does seem to weak to support the weight of the whole unit. You could put in a pneumatic piston or two in there, but the resulting weight distribution would be very unbalanced (entire weight would be on the far edges of the toes), which is not too good when trying to make a walking machine.
BTW I am a total lego pneumatics fanatic; I have all of the double-pressure pneumatics sets (1989-present) and multiple copies of some. I use pneumatics in just about all my creations; the things are just awesome.
The old pressure/suction units were also nice and can come in handy for certain tasks.
Also I forgot to mention this earlier; the render is great, but it needs a title.
