?'s About Cubic Feet

[tigerh4rf]

guys should you use the specs in manual to use for cubic feet the manual says 1.25 per sub or should you start somewhere else designed a box with 8 rf p3 10s box is 10 cubic feet 1.25 per sub port is 32.50 h 22 w 6 L tuned to 48hz should i start the build at this point or do you have another suggestion box is for spl and sb