On our extension build, a curved roof joins 2 separate existing buildings with pitched roofs together. We have the curved glulams installed and the weatherproof membrane on. All we need now is more insulation and standing seam zinc. Of the 3 potential companies to fit the zinc, only one is insisting on gulleys where the curved zinc section meets the pitched slated roof. Those gulleys and the carpentry and leadwork required are going to add significant cost. 2 others are saying it’s no necessary. The company insisting is saying we’ll collect water at points on the down curve where water will pool between standing seam and slates. Has anyone installed a curved roof and got any advice. Thanks.