there should be nothing wrong with the shape you have chosen, if you want to port it, you only option is to have the port sticking out the side of the box.
do a search and you will find many diffent port lenght calculator, or you could dload a program called " winisd", its free.

if your looking for a program to draw up this box try dloading and playing around with "googlesketchup" its a great free program that draws in 3d. you will find that this shape of box will be very difficult to draw, but watch some of the tutorials that are provided with the progam and you will get the hang of it.