...............any roofers out there..........

................We moved a porch up against our trailer.....not much pitch to the trailers roof and even less to the porch........we tinned the roof of the porch with the tin that has a raised rib every 8 inches or so..............the ribs fit under the rain gutter on the trailer, which means theres high and low spots...........so here is my question...how in the hell do we install flashing to follow the contour of the tin.......any and all replys appreciated......thanks ...........kim.............