no!
Your doing it all wrong, if you are going to seal it off have the port and subs face the front. Those dowels would be doing very little, and i am not sure whats going on the the side of the box with the port but it would be very difficult to replicate with MDF for a beginner, and wouldnt be a good idea to have a joint right there in the middle of the box where it will see quite a bit of stress..
you should probably take some accurate measurements of the vehicle and give yourself some room to get it into your vehicle.. that box your looking at loaded with subs would probably be close to 200lbs...