Thanks for the replies.
I'm running this on a Shindaiwa 500 with a 20" bar. Mostly cutting Alder that is already down. As mentioned, the guy that made up my chains ran hot saws but as you said it would make more sense to have lots of cutters working for you if you have the power.
My wood varies in size but if I get into anything that approaches bar length I just grab my step dad's 045 with the longer bar.
I'm not too concerned with cutting speed as I have lots of time to cut wood and more wood than I could ever use.
I am interested in your opinions as to what chain you would recommend as being most efficient with this saw.