The curved pieces for the mansard roof trim were tough! butterflyex recommends installing them before laying shingle templates because they are so tough to hold down, but I think they would've been tough either way because my roof pieces were not quite square-fit... I wanted to lay them after shingles for a neater look anyway... At some point I gave up trying to get the edges to meet, and just strove to tack them to the roof; I have some big gaps to fill now: &#