box design

[PURP's 02 Denali]

so im pretty sure this is going to be a long shot but i just started work and i have little time to learn how to design a box so if there is anyway i could get somebody to design me a good sub box tuned to around 29 30Hzs that would be great as soon as i get a chance i will take measurements but its going in a 2002 yukon denali by the 3rd row seat so not a lot of width. its for a single 15 skar audio vvx-15 on 800 to 1000 watts. and im sorry if i had the money to pay somebody to design me one i would but i dont. if possible for free i would like to have it be the best box possible to get the most out of the sub also obviously its going to be sub up port back thanks for any and all help in advance.