RE designer isnt as accurate as the Torres box calc. TorresBTC.zip (cant belive no one mentioned Torres yet!)
as far as flared ports go, i found it easier after doing about 6 slot port boxes to use the port tubes, yes you have to cut another hole and make sure the port fits but to me it was easier to calcualte the tuning and install it, plus less wood you have to cut. parts express has some nice ports by Precision that i've used on several boxes. do some reading on enclosure design before making anything.. GL