Hi,
i dont got much time so i keep it short 
you can check the CU for V3 SD invoice in TCode Spro (see screenshot below). as far as i know there is no more CU regarding this point.
if output-type is always RD00 as far as i know there cant be different formulars - only if the communication-type (email/fax ) is different you can maintain different formulars for different types (under the same output type)
what maybe can happen is if you test old formulars, they can be triggered with an old condition-schemata. but testing with new billings should be shown with 1 and the same formular. defined in Nace / spro (its the same CU)
regards
