The roof on my Campster
undulates with the highest points at the structural cabinet verticals. (Probably always has to a great degree.) I removed material with a Dremel Tool & sanding bit and added were the "lip" was short (and it was very short at the middle front where water would rush in when if towing in rain).
Mine would have been a lot easier if I had found & purchased a 1 inch bulb seal, as I had to add material in 3 areas. The 3/4 inch was too small for a good seal where the gap was greatest.
I think you really want to get a good seal at this lip. But I did go ahead and also add a foam strip to the inner wood frame, primarily as a dust / air seal.
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