i am currently building a box for my mercury sable. it will house 2 15" ORION HCCA subs. my max dimensions are 17"H, 35"W, and 25"D. i want it ported. the site called for 33 Hz so i am going with that. also 5"port diameter. i do not have enough room on the sides for 2 5 inch ports. can i put them on to instead? if so, how do i achive the 20" port length that i need? PLEASE HELP ME. thanks