I took a quick 3D scan at the back of my house and then loaded Gus into the scene and played around with the scale until I got it about where I think feels right.

At this size, Gus is approximately 46" [1.17M] tall from the ground to the top of his head in this model where he is leaning forward slightly, not counting the ears or the hair tufts.

Accounting for the curve of his tail in this model, he is about 11 feet [3.35M] long from the tip of his nose to the tip of his tail.

I may adjust the scale later, but for now I think this seems pretty good for 3D printing a life size Gus, assuming that project will actually happen.