I hate how the rear suspension travel is severely limited when my car is fully loaded. We need a setup like this except for strut type suspension, but someone needs to spearhead this.

http://www.ride-rite.com/

click on coil-rite

 

There is already a solution: mzmtg's long travel rear strut mounts

http://forums.maxima.org/showthread.php?t=335520

 

thats only for 4th gen. I have a 5th gen.

 

are your bumpstops properly trimmed?

 

I think my springs have weakened. I have had my rear H&R's on for about 100k miles. I just replaced my agx with illuminas. When I had first installed agx and H&R's I never really bottomed out. Do springs lose spring rate?

 

springs dont lose spring rate. what you have is called "springs settling", which takes a couple of weeks - your car will be slightly lower than when you just installed them.