only reason i would do down firing subs, is if i had space constraints and no other way to mount them.port down in a truck feels best to me
I dont know alot about freq. tuning thats why Im asking so plz dont take me the wrong way but from what i've been reading low 40s is for compssubs and ports up around 40 to 45 hertz if you tune it too low the subs wont like it resonant freq. in mine is between 54 and 64 hertz