The Home size is right it just looks small cause he's curled. At 7m length he's exactly the height of 2 Groudon stacked on top of each other. Using the image of the straight Rayquaza and stacking 2 Home Groudon next to it shows the Rayquaza from Home is the same size when you match the size of the heads, segments etc. Sometimes it's hard to mentally visualize how long something really is when it isn't straight.