The 'Warpaint' book on the Fulmar states indeed a 500 lb bomb as an option for the Fulmar II; the Fulmar I was limited to 8x25 lb bombs max, per same source. The 'strike radius' with 500 lb bomb was quoted at 220 miles - quite useful. Fulmar was carrying 186 US gals of fuel internally in a protected tank, for eg. the SBD-1 was at 180 gals, the SBD-2 and subsequent were at 260 gals of protected fuel (only possible with a bomb of 1000 lbs and less).