I'm putting a good preamp in a very small cavity and wNt to order the parts, not including the battery, are any if these units significantly smaller in size? ..Even by a cm or two? Some websites list the dimensions,& some don't. Has anyone worked with a few of them, where they could compare them as far size? Its a 2 pu, 3-knob PJ bass, I'm hoping to avoid a fourth knob by using a stacked control for the 3rd knob. of all the nicer preamps,anything u know that's definitely a space saver?