enclosure help for Fi

[jizazz12 0]

thinking about putting two fifteen inch Bl's or Q's in , but I'm limited for space . I'm working with 17hx40wx28d going to be using 4" flare ports,

question is should i keep the box right around 8 cubes or drop the size down a little to around 6 cubes and what should i tune it to 30 or 37 hertz? the car is a 2005 sonata box will be subs back ports back any help or suggestions would be appreciated.