I bet you could do it, but it wouldn't be easy. The insides are SO reflective. I don't know how you'd deal with where the 'wall' would meet the opening There is almost certainly going to be a gap.

I know you said money is an issue, but how about 2 of the 120's 4x4x7.9? Keep an eye on craigslist, I'll bet one pops up.

If you do try it, don't go 50-50 do 60-40 (at least) so the flowering has more room.