Building this box for L7, good or bad

just remember that your speaker and port takes up air space. i believe they take into accout the port in specs but not speaker. i built one box and was off .45 cu ft and it sounded terribble ended up making a sealed box out of it.  a good size magnet on a 15 will displace .20 or so cubic ft. doesnt sound like much but after my one experiance i started paying more attn to that. EXP: my 3 10's displace .36 cu ft  rottenbellys 05 crew cab colorado.Pioneer dehp 880prs, kenwood excelon in all 4 doors. Bazooka 500 mono Jl 10w3 in coustom center console box.