Well my tunnel will be pretty long. It is 59.5 deep, 30.5 tall, and 43.75 wide = 45.94 cubes then subtract .75 on each side for the amount of space the wheel wells took up on each side so 44.4 minus sub displacement which is 2 cubes so 42.4 then all bracing and baffle displacement (each baffle will be triple thick so 2.25") ill be right around 37-38 cubes. Planning on doing 15 sealed and whatever I end up with ported hopefully around 22ish.