Fade out/Cut off shader at edges?

Hello all apologies in advance as I suspect this is a simple problem but I’ve been unable to find the solution.

I have this material to give this look of rising overly stylisied steam, this is then thrown on a mesh. My issue being the edges of the mesh give an ugly cutoff to the effect, as you can somewhat see in the first screenshot below.

The second shows my material set up, I tried using a second opacity mask on top of the first one but unfortunately couldn’t find a way to work that out either, I just want the top and bottom areas to fade out the material. Many thanks in advance!