I just got back from a 3 day trip and read your comments. My thoughts on this may be incorrect based on what you guys are saying, but here they are anyway...pick apart as necessary! I only have 3" of lift on my XJ, so I want to use the small amount of upward articulation I have as much as possible. I also have open diffs so it is very important that I keep all tires in contact with the terrain as much as possible. I don't remember all of the measurements exactly, but the Daystar bumpstops were around 3 inches long. If I installed them I would be subtracting a portion (although smaller than the 3" due to compression) of my up travel. If I bumpstopped inside the coil then I wouldn't lose as much of my up travel if I measure correctly, allowing for compression of the bumpstop of course. This in turn would help the same side rear tire remain in contact with the terrain better, until the front is high enough to unload the rear suspension enough to allow rear wheel spin.
After reading Goatman's post I got to thinking that whenever I have stuffed a tire and looked at it, I'm not quite bottomed out on the shock. It seems the spring is stopping the compression rather than the shock (as you said).
Soooo, it seems that once again I haven't got it quite right...let's try this train of thought.
In a properly set up suspension the spring should "limit" travel, for the most part. The bump stop is designed to prevent transient movements from forcefully bottoming out the shock, but once the transient force has subsided, the spring will continue to "limit" the suspension movement. If the springs are too soft, you will be bouncing off of the bumpstops all of the time or even resting on them, when the vehicle isn't in motion, at full stuff. If they are too stiff then you won't be taking advantage of your suspension travel and will be lifting a tire on even small obstacles.
I don't punish my suspension at high speed, so this is all slow-speed crawling-over-terrain kind of stuff, by the way...
It's late and it's been a long day...am I on the right track now? Thanks for the input.