Stan;
My chart doesn't have #8 shot listed at those extremes, but does have #7. At the 60 yd mark the 1330 load had dropped to 580 while the 1135 load had dropped to 540 so only 40 fps difference at 60 yds for the 195 fps difference at the muzzle.The # 7 size lost more over the first 20 yds than did the #4 size.
This is all based on two factors, first drag increases tremendously when the speed of sound is passed.
Secondly as all round pellets have the same shape ballistic coefficient is base purely on their weight versus their drag/surface area. Weight of a sphere goes up proportionately to the cube of its diameter while its surface area goes up proportionate to the square of its diameter. Thus as long as made from the same material the larger the ball/pellet the higher its BC so the better it retains speed. A given size of lead pellet though weighs some 45% more than a steel pellet of the same size so retains speed much better. This is why it is necessary to GO UP in size when using steel.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra