I have this little problem using AE : if I use a feathered mask on a colorama effect, the mask acts on the source clip and the colorama effect cancel the feather option. How can I tell the mask to act on the rendered clip?
Here's the problem, this should be feathered (like the second pic) :

I managed to do this by putting the background image foreground and using an inverted mask on it but, believe me, this is not very funny to do... :

Thanks.