(2) 315 CMH scrog sizing?

Been thinking about rearranging some things and building out a scrog net for two 315 cmh lights I have. I am having a hard time deciding on what size to make the frame, 3x6 ft or 2.5x5 ft.

The area will be open on one side to work from (front, long side) and the other three will be painted white.

Any opinions on what size I should shoot for would be appreciated.

From using my 315, I'd go the 2.5x5 route.
I'm sure, if you know your lights, that drop in Lux on the outside 6" of the 3x6 you know is coming will drive you mad.

Would me