dwaasp,
I'm not sure why the 60-70#er I test shot was faster, I just figured my bow was slower. Please don't take my one time experience as science.
I know the higher poundaged Pat shot faster than mine even at a lower weight because I brought in the same arrow and shot it through their chrony both times I shot. (test shoot date prior to order and purchase date).
The 60-70#er shot my arrow at 289 at 62#(their scale), my bow at 65# (their scale) was shooting at ~285.
4ps less plus whatever speed the extra 3 pounds was worth.