This will depend on how long your dives are, and if you plan to do multiple dives in a day. A single dive for 30-40 minutes in the low 50’s F may be OK, but you will not be OK for longer dives, or three dives in a day like that. When the water gets up into the upper 50’s F to low 60’s F a 7 mm is an definite option and quite reasonable at 65F. At least that is the case for me, and you noted different people have different cold tolerances. Generally bigger people tend to be more cold tolerant.
If you are going to do multiple dives pay attention to how much heat you lose during the surface interval. Dry off and wear an ankle length “boat coat” and a hat to minimize the heat loss. Of course a hooded vest, gloves and booties will be needed for the lower temperatures.