Effect of draw weight on arrow speed

[gzg38b]

I'm currently shooting a 70 pound razortec, cx300 arrows, and 100 gr tips. I can shoot one pin out to 30 yards. If I back my bow down to 60 pounds, could I still shoot one pin out to 30 yards? How much arrow drop would I have at 30 yards? I've read than10 pounds =20 fps. How much would a 20 fps speed loss affect arrow drop at 30 yards?

[goldtip46]

if you have your pin set at 20 yards then i would set it at 25 and try it to allow for 20 and 30 yard kill zone.

[Barth]

you will need to raise the pin cause it will be probably a 3-5 yard change