helper springs/add a leaf?

I have been doing some light towing lately and noticed that the rear end sags quite a bit.  Iwas wondering if anyone has used helper springs or add a leafs.  How well do they work and which ones are good
 
 
2001 Blazer LS
4x4
4.3L

those are good helpers or a stronger leaf pack made for it or you can go with a helper rear bag setup it smooths out the ride and levels you out under load.

I put some rough country add a leafs in my 91 blazer it helped alot but it did seem to stiffen the ride a little bit 

Try http://www.activesuspension.com/.
 
I used a add a leaf on my 94 blazer and used this on my 00 blazer.  No comparison and easy to install.  I bought mine on e-bay.