It was a very good try, but what you missed is that the bit of the rectangle CLOSEST to us is going to be bigger than the bit farthest from us. So in this pic, his head is much larger than his ass when it ought to be the other way around. Actually, the way you drew him, he bears a striking resemblance to one of my dogs, who we call 'Tadpole' because his head is so big.
Haha, perspective is one of my biggest problem points! I can draw all kinds of things from a side view, but any other angle has been nearly impossible xD but this should help a lot, I'll give it a try! Thanks!