Help with physics

[sicklebrick]

Firstly, apologies if this is in the wrong thread, or has been covered before, but I'm not sure exactly what to search for...

Anyway, I built this spider using wiremod: [img_thumb]http://sicklebrick.com/hotlinks/smallspider.jpg[/img_thumb]
It's all wired up, programmed, and the legs work fantastically well - as long as it's suspended in the air.

On the ground, the physics begins to stress and bend, and twitch constantly (Called spaz?).
I read somewhere that increasing the weight of the props (I used Weight STool [sic]) can help a little, especially if you branch the weights out like a tree.
I.e. As you branch out from the center, make things lighter.
This works for the first few joints but the lighter ones begin to spazz, and increasing too much means I need an unreasonable force to hold the thing up - eventually it's too heavy.

I also tried:
-Welding all of the base plates together
-making lighter stuff in the middle, heavier on the outside
-using multiple welds
-using multiple weld types (i.e. a solid and ballsocket next to eachother)
-using the robots parts pack (this was *much* worse)
-upping the physics solver iterations (not available on public servers either)

Each leg has a knee joint, a hip joint, and then the rotateable one you see.. since hip was taken, I called it 'arse'. The arse is welded to another table prop, and that's welded to the plate.
(There's also a beam on the arse stopping it from swivveling too far, and a bunch of ropes set just above the maximum distance for each extension/contraction. )

Am I expecting too much of the physics engine here?

Honestly, I'm just amazed people can manage to build stuff like this:
[img_thumb]http://sicklebrick.com/hotlinks/bigspider.jpg[/img_thumb]

If anyone has any advice here, it'd be really appreciated - my poor spider's lookin' a bit dead (and quite cool, but still dead) - [img_thumb]http://sicklebrick.com/hotlinks/deadspider.jpg[/img_thumb]

Thanks,
J

p.s. Anticipating that this place is full of pedants and knowitalls, I'd like to point out that I know fine well how many legs spiders have. It just made more sense to start with 6 legs, and have a stable tripod on the floor constantly.