RE: How lite is too.....
Something else to consider is what specific setup in terms of draw length, draw weight, etc.. you are shooting the bow at as well as the amount of energy that the bow generates for any given arrow weight. There is a big difference between shooting a 60 pound Hoyt Protec with Accuwheels at a 28 inch draw length with a 5 grain per pound arrow in comparison to a Bowtech EXVFT at a 70 lb draw weight with a 30 inch draw length and a 5 grain per pound arrow.
The difference being the amount of energy that is released into the arrow.