Does anyone happen to know how thick the wall is by the door to the head (the wall facing the companion way)? I forgot to measure when I was at the boat so I might have a 2.5 hour round trip just for some screws for my new hatchboard holders. 
You are too kind! Thank youMeasured mine today and it is 3/8 or 10mm.
Went back with my glasses and in fact the head door thickness is "exactly" 13mm.You are too kind! Thank you
I thought 3/8 was a bit thin. 13mm in our old english measurement weirdness is 1/2". All that said I'd bolt those onto the wall with nuts and washers instead of merely using wood screws in material so thin.
Just a thought, Mike