Anamorphic flare shape

I'm messing around with the BloomAndLensFlares Pro Image effect. It's the only way I have found to make an anamorphic lens flare. And the way its showing up is as a big fat line with slightly rounded ends. I would like to change the shape to something much thinner and with more drop off in size as it gets to the ends.

How do I change the size/shape of the flare generated by this script? or should I be using something else?