Using a HVAC software program I calculated the heat gain for my house to be approximately 32000 BTUs. However, the software for some reason won't let me change the outdoor summer design condition. It defaults to 105 degrees and I think for my area the recommendation is 91 degrees. I'd like to add a little buffer to the program of 7 degrees. My question is, approximately how much would the heat gain change from 32000 BTUs at 105 degrees to 98 degrees. Would it be enough for me to want to go with a 2.5 Ton versus a 3 Ton?