Whenever it's a ver erratic pattern, I always look first to fletching contact, then to something i'm doing in my follow-through. With the higher profle of the Blazers, the contact issues can come about where there used to be no issue with a standard vane. It's odd that one style of Blazer would be so different though. The Quickspin ones do slow your arrow down SLIGHTLY, which would not account for 4" of drop though IMO. Hard to say, but at least you've gotten it ironed out!