thats what happens when you use 4 small aeros to gain a low tuning. any sub will likely move alot.. as with my P.O.S cvr 15 in a 2.5cf box tuned to 31 with a single 3" aero powered by a PA amp off no power,bish moved like no other and got down for what it was.
none the less i bet it sounds good when ya shut the hatch and let it load