Mine was cracked in the corners, The dicor created a dam that trapped water. I just filled the void with dicor, sloped to drain and it lasted 5 years till the skylight cracked from being sun rotted. It took 5 hrs to replace the darn thing, 4.5 to remove and clean the dicor and butyl caulk off and .5 to install and recaulk. Have the dealer do it.
2016 Chevy 2500HD LTZ Crew Cab, Duramax
2005 Terry 270FQS
2006 North River 20' Seahawk