bigger port area to compensate for available ft3

[anubis]

The current enclosure I am running is a hair over 6 cubes with port thru rear deck and with small port area (10.5in2/cube). In order for me to get bigger port area I would need to shrink the box of course but how much port area can I get away with? minimum and maximum in reality? I know the reccommended is 12-16in2/cube but will going any larger bring down the effiecency of the woofer? Net with large port area would be in the 5 cube range (low). Any suggestions would be appreciated.

[anubis]

gotcha and thanks