I just went with personal preference, out of all the other lid's I have, the ear cap's all appear to differ in dimensions/width's to some degree.
So I just trimmed away until I was happy with the overall look, roughly 5mm to the front of the cap's 3mm to the back. this is a rough estimate
Hope this helps
PS starwarshelmets is always a good reference site for Accuracy issues & you get to look at loads of cool pic's