[Brim only on the outside of object?]

Trick you could do, is disable the brim. Set the skirt lines to 30. And set the skirt distance to 0.01

This will generate an outside only brim (as you trick the skirt code, which is only on the outside, to acts as a brim)

 

I can confirm that these settings work, although 20 skirt lines might be more than enough