RE: Optimum Speed
Slow well fetched arrows are not a big deal, actually prefered. However like said, when you get to the faster arrows they can be tricky to tune. Not that it can't be done, they are just not as forgiving.
I honestly think most of the problems with fixed blades and high speeds has more to do with arrows not having enough FOC or enough fletching to control well in flight. Or maybe spine issues as well.
Paul