first real sub box. checking recomendations

[ncc74656]

I am having my first ever sub box built by a friend of a friend who useto do installs at circuit city. I have ordered a FI BL 18" and this is what he has thus far recommended. id like to know if anyone has any insight to what he has said.

1" MDF with a down firing sub and vented to the back. tuned at around 32hz, i would be cutting my back seat in half to fit this type of box. it will be going into a 2500 dodge ram quad cab 1999. cost wise ive been quoted 300-425.00 for the build.

i kinda want to be able to see the sub BUT i also do contracting work so perhaps it would be safer to have the sub face down. im told that a down facing sub will have more bass and get louder with better clarity than one facing forward or up.