I am going on vacation. I cant have someone come to my house to pet sit so the rats(x2) have to go to a friend while im away(about 4 days). I obv can not bring my critter nation to my friends house so I have a kaytee brand travel cage large enough for a hammock, a wheel, and a house. My bigger rat(400g) sometimes picks on the smaller(250g). Never aggressive, and never injury, just dominant badgering like "oh your in the hammock well not anymore! Now its mine!" Any the smaller is just like "ok" and goes to a different hammock. Dont get me wrong I find them snuggling all the time, its just that the larger likes to throw his weight sometimes. With a smaller cage im affraid the badger may escalate if smaller has no where to go. So I want to cut a hole in a house small enough for mr smalls to squeeze into but too small for mr bigs to go in. I have no idea how to measure on a rat for that kind of thing and have limited material for trial and error. Should I measure shoulders? I fig if they can get shoulders in then they can get the rest in, or is that too wide, should I measure just a little bigger than their head?