bought a optixs G5 ME sight need to know arrow speed to set up the pins.need helpfiguring out the speed. thanks
bowtech patriot 70LB
28.5 DL
maxium 350 29in long with feathers

I was planning on changing from feathers to vanes and should I cut the arrows shorter? thanks

The only way you are going to know the arrow speed is to shoot through a crono.

absolutely. find a chronograph. Any other way is just a guess and can easily be off by 30 fps or more.

Forgot the second question. If you switch from feathers to vanes you will have more weight on the tail end of the shaft, thereby making the dynamic spine stiffer. Cutting more from the shaft will make it even stiffer. At best you'll have to retune the bow/arrow setup.

And as for the initial reason to know the actual speed: I wouldn't recommend setting them from a chart the relies on speed anyway. Too many variables. You will get fairly close, but actual shooting at the range is the only way to set the pins.