fok that's a big tent
you gona need a lot of light for that size tent, if you get only one of the 240w qbs you'll only have round about a 1mx1m of decent coverage in that space, and theoretically it'll be even less efficient, because in your tent the light wont have the reflective walls at the 1mx1m border to bounce back off of, so you will "loose" that light off to the sides. this is the whole point of the reflective insides of the tents.
you can always add lights as you go, which is nice when working with those small qbs, they take up very little space, easy to work with and all that so you can hang a lot of them with ease.
I would also say at least 3 of them in that tent and 4 max, you can play around with the dim and brightness settings too if you get the right lights so keep that in mind
excited to see you put the setup together!