ok if you want to know what it is I'll give you a riddle to solve that will reveal the mod..
Take the diameter of the 20" wheel and times it by the size of the 23 sq inches of the dog house.. when you get that answer you times that by the 23rd letter of the alphabet
When you get that you count backwards from one hundred six thousand until you find the Sq root of 24.. then and only then remember back to the first thing I ever posted on 1 of the 3 different forums that I belong too and count 12 post ahead of that...
Then you will know...
After wasting all that time making that up I could have just told you guys........
But where is the funn in that