Sound deadening & TIPS

[Megavanman 2]

hey whats up im new to spl, i have a 94 ford econoline van i have competed in spl for 1 year this is my first , and i love it, i have 4 l5 15's im puttin in a box, the box will have 13.3 cubic feet of airspace i do not want to wall but i want to be loud, i was thinking about sound deadening my roof and floor basically everywhere is it a good idea or no, i was also thinking about removing my middle row of seats, to let more air go by, any hints or tips on making a van loud without walling, or any tips on what i should do , thank you