I've rebuilt recently an Ibanez rg with an Edge III tremolo, which is well known about its tuning stability issues.
After reading many threads and reviews, I've decided to buy this Goldo backbox. Although many people are stating that one is enough (maybe it is), I've bought 2, because I didn't like the idea of positioning the springs or the backbox asymmetrically. In my current setup I use 3 springs (1/3/5 positions), and 2 backboxes between the springs. I also installed a Schaller sure claw. Took some time to fine tune all the springs work together, but I'm absolutely delighted with the results. After many days of use of the tremolo, the tune is still almost perfect.
The quality of the product seems to be solid, I had no issues whatsoever.
I really recommend it, does magic with the FR style tremolos.