Actually, CV is hard coded as 1 attachment - you could make it possible to attach other types than CAG, but it would make CV's pretty pointless otherwise.
And I believe you can actually set CVL's up with 1 attachment - just that their current unit file doesn't allow any attachments. The exe will allow them to have 1, however, AFAIK.
In terms of where this is coded, it is in the exe file, I believe - not a "game moddable" variable, unless you go play with the exe.
Tim