Here is an entry made in my Chuckwagon thread back when.
Was ambitious last night so I trimmed the excess material at the hinge point of the hatch. I used some 5" wide ice dam tape over the 2 edge of the 2 sections as my 1st water barrier. I then applied 1/16 " black neopreme rubber cut to six inches wide. I bloused it loosely over the seam and installed 2 sections of 1" by 1/8" aluminum flat stock. This flat
stock had been drilled to simply screw thru and secure the rubber membrane.



Note that the deflector runs long and the dog ears allow the water to channel
away from the sides.
I have 4 builds all done this way ! No runs no drips no errors !