1 6"pvc port enough?

[icweiner]

is one 6" routered pvc port enough for a 4.2 cube box tuned to 36hz for 2 cvr 12's? reason i am asking is because i am tired of building slot boxes that are huge and i can never line the port up perfect and i want to try round ports

[mlstrass]

6" port gives you 28^2 of port area, so it seems on the small side for 4 cubes...