I do not think this test proves much for any ship in terms of interplanetary travel. It ignores possible factors, such as the Sun's gravity, possibility of larger planets with higher gravity than Kerbin, not to mention planet surfaces and atmosphere... You assume alot saying Kerbin will still have the toughest gravity and thickest atmos. However I think if you can do the following with stock KSP... regards from me. Travel from Kerbin land on Mun. Leave Mun travel to within 10,000,000 of the Sun. Travel back, land on Kerbin, take off without restarting or refueling, land on Minmus, and then travel back and land on Kerbin. Think you should be good for most of the planets then... Except maybe the one planet that is so close to the Sun it is barely visible