Need gem, create a fanrasy creature based on dogs.

firstly, i didn't know where to go, sorry if this the wrong place.

I am not a dog owner, but i do need help of a soul who know about dogs.

First off all i am writing a fatasy work and i am creating my creature, but i have a creatured thats a mix of Samoyed/English Mastiff/Azawakh.

The animal is called a lunathor, it has the long skinny legs of a Azawakh.

but the body of the mastiff. and the tail of the Samoyed

What i need to know is; is there a specific body length (without the length of the legs counting). if their are no specific lengt, Perhaps a esteamtion.