In VLN Regulations 2012 is written: the max. fuel capacity on board is indicated for each model in the classification list. This max. fuel amount includes tank, filler neck, pipes, catch tank and additional FT 3 Tank.
It is permitted all these tanks to mix up to the amount mentioned in the classification list, i.e.
FT safety tank (large) with the total amount; standard tank + small FT 3 Tank; standard tank only; Catch tank can be added to all combinations, but not to exeed the max. amount.
The standard tank may not be extended, but existing tolerances can be used.
Klaus von Barby, VLN regulation and technical
