the low notes move more air, causing the flex
tune it to whatever you want. what made you point out 32 and 27 hz tuning?
and...i may be confused, but if you were gonna tune 2 boxes to 35 hz...why would you wanna change the tuning of one big box?
and we really cant help you with a box until you get dimensions of the back area. we can make a general box, but then it might not look right in the car. also play better if we could utilize your space better. so...if it were me i'd say you'd just have to wait a couple months or whenever till you get it.