That's why arrow drop numbers are completely bogus. They don't tell you anything you need to know in the first place, and a lot of folks come away completely confused after looking at them. Shooting perfectly level with the ground, off a cliff? C'mon! Who does that often enough they'd need to have it calculated?
Just ignore the arrow drop stuff.
Trajectory is what we need to look at. Jackson still has a link to Andrew Middleton's graphing trajectory calculator on his site, but the link is busted. I haven't been able to find it anywhere else on the net, and I've desperately hunted for it. Excellent tool. It works real well for making sight tapes for single pin sights.
I'm eventually going to have to break down and buy one of the super spiffy archery programs so I can have everything I need right here, and not have to worry about sites shutting down. [&:]