Hi Chris,
We touched on this a week or so ago when you posted one of your photos. By introducing a rule which says a ship must have a certain percentage of reefer space to make it a reefer runs the risk of over complicating a site such as this. Most people (and this is not a criticism) will probably not know the ship's capacity detail when uploading a photo, so I'm in favour of trying to keep it as simple as possible. I said at the time that only pure reefers should be in the reefer category, until you pointed out that the Patricia U had some non-refrigerated cargo capacity. In reality, Patricia U was primarily a reefer and was operated by a company specialising in such trades (at least in her later life). I stand by that really and say that ships which are PRIMARILY reefers should go in the reefer categories and general cargo ships with part-reefer capacity should go in the general cargo category. For some of these old ships, if you have access to old Lloyds Registers, they are pretty good at distinguishing between the two types and that would be a good rule of thumb to use.
Brgds
Phil