>1kt with all stock, ~1600 parts, 14*5 Mainsail boosters with 140 Jumbo-64 fuel tanks and payload is - 49 LV-N with 28 Jumbo-64 (~12km/s delta-v) But such amount of fuel and ship itself is pretty useless. Most fun was achived in construction time, so since i am using FAR, it makes sense to rebuild it with proper aerodynamics...