Single stage to orbit with plenty of fuel left to deorbit. If you really wanted to stretch it, 3 fuel tanks is probably doable if you pilot it ideally. I don't think it's possible to get much more minimal than this. Good job, people really over estimate what they need to achieve orbit. Unless you can get a lot more thrust, adding more fuel has diminishing returns. SAS modules are for sissies. They give you a huge performance hit. Agreed, I've never needed SAS modules.