I want to get a harness for Atlas. I was looking at the aviator harnesses but I'm not sure what size to get? If I go by weight (71 grams) according to the chart I should get an XXX small but the suggestion for a GCC is listed as a XX small. Should I go with the XX small in case she gets bigger(she's 8 months ish) or go by her weight? I don't want it to be unsafe but I also worry about it being too small