i have an 86 seville cuddy...i know its no fishing boat but it works for me. i would like to mount some kind of rod holder in the cabin. are the inside walls of the cabin thick enough to screw into? or will i be risking putting a screw right through the hull. are the walls and the hull one in the same or are they actually 2 different "walls" ..... what i really want to know is how thick are the inside walls?