want to cut the back cab wall for subs

well i have been thinking that i want to put a system in my truck again soon and if im going to go through the trouble, i might as well do something worth doing, i want to cut the cab wall and do an encloser into the bed . when i am all said and done i want two 12" w7's flush with the inside of my cab back wall . i thought of making up a steel box with one open end which would be the end facing the back of my seat my question is would the bass vibrate the steel and sound like shit? or should i make it out of something else, keep in mind this truck is driven almost daily and it has to be water tight i wont have a tonneau cover on my bed. does anyone have pics of some set ups they have done in the beggining stages, not pics of finished set ups but some pics of start to maybe half finished or to finished. i want to do my own design, but ideas would really help me. thanks for any help