Penetration can have a LOT to do with choice of arrow weight and a ton to do with broadhead choice, correct choice there can make up for weight issues quickly...
As to 300 and above, sure it gets squirrely, and its NOT new either, just the speed issue is a bit new, we used to do it way back trying to shoot light enough arrows to bump speed.... found out that penetration was lost, the ping pong/vs golf ball thing, and that it got really squirrely spine wise vs accuracy. Same thing goes on there in high speed, IMHO, you have to have X bow, and X arrow and if you have trouble, simply get more spine via more arrow weight, you solve the problem but also drop below 300 most likely.
The other issue involved is that until arrows are around 1200 fps there will always be the noise factor... that noise factor cries for closer shots to be sure, not the 30-50 yard flings I see on TV a lot. Most every one of those deer is moving before the arrow hits, WHY take the chance?
