It is pretty common practice to mix up some microballoons and epoxy to glue the hinges down on the cowlings while they are also riveted. This has the advantage of filling the low spots so that the hinges don't have a lot of bending stress in them later on that would cause cracking.

I went a little overboard, when I did mine. I discovered (too late) that you only need a little bit of the stuff. If you get too much on there it oozes out all over the place. Once it cures it makes it difficult to get the hinge pins in and it can get in the way of the cowling halves fitting together. Put on a nice thin coat and then rivet the hinge on. If you get a lot of seepage then you are using too much.