Well again, if you slow bow, and then lighter arrow, your drop will be the same, as even you say, in your example, first shot, then after your example, it would hit same hole
thus, your gap wouldn't change, and all you did was lower draw weight, and lower KE of the arrow
so to be fair, I see your example as being a wash, and not changing anything really on drop down range!
I have shot 1,000 yrd matches for close to 25 yrs, so my logic goes more with guns
but again, if you adjust, compensate lighter arrow, to get same speeds as with heavier arrow, and higher draw weight, it to me would be a wash on drop
a 500 grain arrow at 350 as to a 400 grain arrow at 320, just crazy numbers
the drop down range would almost be the same, thus, pins shouldn't change?
only way I see to get pins farther apart, is again, smaller pins, or change there zero's, from like 20 to 25 yrs or 30, to like 35 to 40, and so on
the easiest and best solutions I say is a one pin sight you adjust for range?
then you do not have to maybe re tune your bow, all the more so if you like your current draw weight and set up/form
and I agree, 70 lbs is not needed for deer, or even bigger game, but like they say, dead is dead, bigger weapon or smaller, shoot what you like and have confidence in
and I am not trying to bash or turn this into a major debate, just asking and stating what I THINK, and just my opinion, and I am NO expert
so don't get all excited folks!