SMALL VOCAL BOOTH .....HELP

Just found this forum,Im very happy.So much knowledge so little time. Im addicted I cant stop reading....but anyway... I have a half a#* set up in the attic of my brothers house that Im try to make not so half a#*. My brother surprise me with a vocal booth a few years ago I was very happy at the time but I now realize that it is way to small 4-4-7 .I know,I know the cube shape sucks. My question is- I can make it little bigger length and width but not higher than 7ft.I just bought some 703 to make some basstraps and was going to line the booth with it as well,its already has auralex 2in foam in it. Will the 703 make a difference.Should I use both. Also, since the booth is going to be dead and small either way due to the circustances would it make a difference to make the booth 5-6-7. One last question should I keep the window or will it cause to much reflection ,it is angled down. thanks for any advice

there's a pretty cool vocal booth design here another one is here maybe that can help you.