sub enclosure joined into truck bed

If it was an SPL truck, I would just say get a welder, and a sawz-all and go to town, but by the sounds of it, it will be a daily driver. You need to keep the box moving free from the cab. You need to create a grommet to go in between. I have only seen one in person and up close once. I am not sure how exactly they fabricated the rubber grommet to go inbetween, but basically, you cut out a hole, reinforce around where you cut out, put in the grommet and seal it, then start to build your box on either side. If you are running your subs free air, then all you need is a mounting plate in between, and the back of your subs will be viewable from the trunk bed (of course you will need a topper or something to shield from the weather) Or you could build a box, then put plexi glass on theback to show the subs.

i have a customer who has a seamless cab and bed.... they've been joined for show appeal..... do you think i would suffer any consequences if i were to cut out the cab and bed to put a box through them?..... would there still be any flex? and would the glass deal with it without breaking?