Thanks Bubin, wasn't aware of Frapps, it works brilliantly and gets around the problem that my model crashes about 90% of the time when I press the reset button. So even with the ability to save the sketchy-replay to jpg's I'd still struggle to get to that option before it crashes. The only issue with Frapps is you can only save the screens' resolution, so I've had to rearrange the model abit in a higher resolution screen display to get a decent result. Still much easier than frame by frame saving.

Thanks Wacov, your suggestion has helped me resolve my problem. My earlier post is incorrect, setting ballast blocks to the 'ignore' state does eliminate them from the mass of the overall group, so the joints do go flexi. However using the overall group shape as default seems to get around the unwanted collisions provided any colliding sub-groups are set to 'ignore'. I can now place my ballast anywhere because although the overall group can be huge its not getting used in collision calculations. Another property of note is that the largest ballast needs to be concealed within the connected group, NOT the group containing the joint itself. Many thanks, I don't think I would have worked that out, definately not in the short term anyway.