Filets do go under tape when you're glassing an entire boat etc. - so the glass can travel in one piece without air entrapment in the corners. In the case of the coaming, the glass is needed to bond the multiple vertical strips. It does nothing as it goes over a filet as far as strength compaired to the filet itself, and... it just creates another fairing chore where the glass goes over glass. It's wiser to do it the way I said and just add the fillet over the junction - no fairing of the glass overlaps and the fillet creates a tremendous bond as well as vertical support to the coaming.