Really depends how far you are flying if you are going from lands end to norfolk then maybe you need to look at different boxes but a qxc flight two should be adequate .
YOu will probably find that the answrr wouldnt be too far removed in any case . try it and have alook
I only ever used two for cpl and never had much of an issue . Just remember it is never so accurate that you can rely on it totally . Once airborne you can assess how accurate it is .