Well ok first of all 3600 btu's is not a .5 ton, it's just over .25 ton lol, and you can google all you care to, I do this for a living lol. You said it's better to over size a chiller and it's not, it's better size it properly and that is not by using an aquarium sizing chart it's actually figuring out what is needed. You know math, it's actually quite easy as 1 btu cools 1 pound of water one degree in one hour. There are actual sizing apps that allow you to punch in your lights, ambient, pumps, etc and they will give you the size. Again you stated it's best to over size a chiller and it's just not. Come to one of my classes and I'll explain more in depth as to why not lol.