Well, give me all the exact measures of the box and i´ll tell you, just remember something, cutting down the lenght of the port it´s gonna raise your tuning even more, not the other way around. By the way, 16" long for a 1.5 cubic feet box it{s around 50 hz, so i guess he´s right about the specs he gave you, i think it´s time for you to try a bigger and more efficient box, if not, well, for a 1.5 cubic feet box you need that external port around 22" long to get a 44 hz tuning...
This indeed was a very good thread with a lot of things I decided to try for fun.
thanks a lot all friend