try some thing like that to change checkbox location, I am not sure it will work or not but try once
ckBox.Location = new Point(rect.Location.X+1, rect.Location.Y+1);
If it works fine give me your feedback.
I have doubt while changing the size of CheckBox. As per my knowledge you cannot change size of CheckBox, I may be wrong. To verify the same add new CheckBox control on Form and try to change the size of same if works there it should work here as well.
If you have any other query revert back to me.