Kanatis do like heavy arrows. I shoot a 525 grain arrow with my 46# Kanati, in fact it's the same setup I use with my 50# Orion recurve. They aren't cut past center, so a little weaker spine works for me. I'm shooting 500s with a 100 grain insert and 175 grains of broadhead up front and cut to 28.5" BOP. I do build out the sideplate of the Orion a bit to make the same arrow tune with both. I paper tune them and both leave a nice bullet hole with three little cuts around it. I draw about 27.75" to 28", but I want the back of my broadhead to touch my finger, so I like the arrows cut 28.5". My fingers aren't very big.
Man, that 58# Kanati should just smoke an arrow! My old body won't tolerate that kind of draw weight anymore, but whitetails are the biggest critters I hunt anyhow, so my 47# works just fine.
I agree with the guys who recommend a test kit. Those calculators will get you close, but it sounds like you are right on the border. Close enough that you're going to want to do some real world testing.
Let us know how it goes...oh, and pictures of the Kanati when you get it are mandatory!