MarkT:
Add it from the 5V pin to one of the ground pins. If its too big a capacitor its conceivable the USB supply could trip out (more likely for an actual computer/laptop than a wall-wart supply).[BTW there is already 47uF on 5V rail on the standard Arduino]
thanks for your help. ill give it a shot later today and post results.
Here is the original thread with my issue for reference.