Something I forgot from that setup was the wheelbase shims, as I'm now using alloy suspension mounts. Currently on both the front and rear I have 3mm in front of the arm, and 1.5mm behind.
Doing some more measuring up, that brings it smack bang upto the same wheelbase as the 416, but with a more rearward biased weight distribution (cells are about 2mm further back). So something else to try maybe lengthing the rear wheel base slightly more... adding that to the list now as well
Cheers
Ed