A ft^3 is a ft^3 right save displacement, if a woofer calls for 1ft^3 it doesn't matter where the driver is placed right? top bottom front back it still meets specs right? [^]=[v]=[>] =[<] right? also in a dual driver do you need to compartmentalize each driver? or is big open center ok? and will a brace affect airflow/performance (if the brace's displacement is acounted for?)
Typically braces are small and we do not need to take into account the volume they displace. And it also does not matter where the speaker is in the box. As far as whether to seperate the woofers or not will get you more than one different opinion. Here is mine, I like two speakers per enclosure. The larger volume helps overall performance. We typically get a lower louder bass from the larger enclosure.