For the galley gutters, I cut a 29 degree angle template to rest the lower section on as I tacked it in place. Wasn’t too difficult, but as others have mentioned, I don’t understand the gat at the sides of the upper gutter where it transitions after the cut channel. I filled it with thickened epoxy, as I filleted the underside of the rest of the gutter. Glad those fillets won’t show!