Last December I installed JCW's 7 leaf rear and 4 leaf front springs. The rears are working great -- no problems. The front right has already collapsed! One run through dusy is all it took to trash it. I'm running SOA so the springs get more compression than a stock setup. But my stock front springs did last 3 years in the same SOA configuration.
The front and rear springs were made by different companies. Don't remember the name of either.
I replaced the rear's overload leaf, which is straight, with a curved overload leaf before I installed them. The straight leaf looked like it would get caught on every boulder on the trail.
I think high5 had a better idea using 4 rears, wish I had thought of that.