The SBD is a 2048 res skin.
AH3-era skins (TBM-3, Ki-61, Bf 110C and G, Me 163, F4F-4, FM-2, SBD-5, D3A and B5N2) are either 2048 by 2048, or in the case of multi engined bombers (Ar 234 and Ki-67) 4096 by 2048. Prior to that it is 1024 by 1024 for everything except big bombers which are 2048 by 2048.