I always went between 2mm and 4 mm longer depending on which nipples are to be used but in this case with the brass nipples i went 2mm longer...........they just bite better than the alloy ones ( although the colours aint as posh ).
My beer scoot has a snowflake front on a HOPE ultralite, with bonus anodising - circa '94?? If they're coming into 'retrovogue', I'd better move frames...!