how much power do they put out at 1 ohm?
Try a high freq with that box tuned to 41hz, like 55-60 cause i do a 146.1 legal with my trunk car and the trunk isnt sealed off so try a higher freq to probly gain a little more spl.
Get a cd with every frequency and then just test to find your freq. Dont use a sweep cause then you look like a nub //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
Good job though id like to see what numbers you put up with this...