Ok i made an account to ask one question :P. among the parts B9 offers the y adapter (protective cap) and if you select the sub part battery it has a ludicris volum of 512,000 capacity. so i think this is way overpowered. I nerfed my own part by changing the base volume from 36 to 6 giving it 12,000 volume. It makes any fuels useless but lets be real here a 512k battery for 30 kerbal dollars is kind of overpowered . i dont know if there is anything you could do to make it balanced either : (