help w/ enclosure sizing

hey, im planning on making a sonosub....

24 inch dia tube...
adire shiva mark iii...
external ava250...
4 inch flared port...

now ive tried running winisd and lspcad, but i have no clue what im doing... like adding polyfill and wall damping foam, and as well as sizing the enclosure...

can anyone give me some help figuring out a good size to make my sub....

im probably going to have a 3/4 incd plug in each end of the tube along with a 3/4 inch cap on the top for a nice finish... downfiring sub and a downward opened port...

it will most likey use it for home theater.. i dont have audiophile quality equipment, but i still want it to sound good.. something for mainly HT but some music...

if anyone has the time to throw together some numbers for me i would be very appreciative!!

~thanks for any help guys....
~mike